Welcome to Hyperfixation Investigations, the podcast where two neuro-spicy best friends take time each Saturday to info-dump their research deep dive of the week.
Lovingly produced and copyrighted by Wolfenstag Productions.
Today's fun fact is 10% of the world's carbon dioxide emissions are stored in soil.
Good morning.I'm Josh, and I will be presenting this week's episode, Roots, An Introduction to Root Structures and Mycelium, part one of our mini-series, The Deep, Dark, and Dirty Depths.
Good evening.I'm Cara, and I'm just along for the ride.
For those of you joining us for the first time, how things work here is Josh will be leading us through a mini-lecture on the topic in the first half so that we can discuss today's topic in depth in the second half.
Expect tangents throughout. We switch off duties each week, so next week expect Cara to helm the episode.
Now to our regularly scheduled program.Josh, what have you been hyperfixating on this week?
Well, Cara, I've been hyperfixating on the structure and function of plant roots and the similarities, differences, and connections between those systems and the similar structures found in fungal mycelium.
That's like mushrooms, right?
Yes. I know a lot of people sometimes forget that plants and fungi are different things entirely, or people think of fungi as like a subset of plants, which is not true, but we'll get into that.
Or otherwise thinking of them as being more similar than they actually are.But I really want to start at the roots, so to speak.
How many puns should I be ready for in this episode?
Not as many as I would like.If I had more time to think of puns, this place would be riddled with puns. So I'll start with plant roots and we'll move on to fungi later.And then we'll get into a fun little connection after that.
And maybe even some science drama.
Oh my gosh, science drama?
A combination of my two favorite things.
Yes, science and theater.A.K.A.drama.
So first things first, before even discussing how plant roots actually work, I want to specify for this segment that I'm primarily talking about the root systems of vascular plants.
There's a lot of variation in some of the finer details, so I'm going to be talking fairly generally, but I'm focusing on this group of plants, this clade, because the vast majority of land plants that probably come to mind for most people when they hear the word plant
fits into this category of vascular plant.
Vascular.So that reminds me of like humans have vascular systems too, right?
It's fairly analogous and we will get into that.Okay, cool.Yeah, good catch. And when I say clade, a clade is a term within the field of biology for a grouping of organisms that have some common ancestor.
So all vascular plants are descended from one common ancestor that pass down the trait that marks them as vascular plants.
So we're talking about that grouping here.Things like trees, bushes, ferns, grasses, flowering plants all fall under this classification.
So does that then include like fruits and vegetables?
Yes.But we're not talking about mosses or algae.Those are very fun, but oh boy, those are very different things. Now, how to actually begin discussing plant roots.Let's start with their purpose.
So plant root systems serve multiple purposes, right?One of which is to anchor the plant in the soil and anchor the soil around the plant.
We love it for erosion protection.
Exactly.A well-rooted tree with large and complex root system is itself more sturdy and less likely to fall over or be ripped out by a strong wind or water's current.
And the soil held together by those roots is also less likely to be removed by wind and rain.So most riverbanks are largely held together by plant roots, preventing erosion from acting too quickly, changing the bank of the river.
Even just grass does a phenomenal job at this.
Roots can also function as places to store energy for later.
This is exaggerated in some root vegetables, like carrots, where they act as a battery to store energy, usually in the form of starches or other complex carbohydrates, so that the carrot plant can store this energy and regrow after winter from that carrot.
And is this ability to hold more of the starches and energy part of what makes things like vegetables good for us?
The fact that they store energy chemically in the form of starches and complex carbohydrates is part of why they're so great for us, too.
Because we get, of course, our energy from eating things that have that chemical energy.Also, fun fact, wild carrots are also known as Queen Anne's Lace by their flower.
Oh, so that really pretty, like, little white flower that a lot of people have in their wedding bouquets or whatever is actually Carrots?
Yes, it's wild carrots specifically.Huh.And funnily enough, do you know where I learned that?
Oh gosh, do I want to know?
Because as you ride your horse around this wild west world, every once in a while you see, ooh, wild carrots.Pick it up, feed the horse, horse is happy.And you see it and go, oh hey, that's, that's Queen Anne's lace.I know that.Huh.
Anywho, just a random fun little connection.Love it. Deciduous trees, being trees which drop their leaves in the winter, also use their roots and inner bark as places to store nitrogen and carbon during the winter.
So while they have dropped their leaves, they store some of that energy in their roots and bark.
They actually pull the nitrogen and carbon out of the leaves during autumn and store those nutrients to help grow quickly in the spring for those new leaves.
Is that part of why the leaves turn colors?
It's an oversimplification to say yes entirely, but it is one of the big factors for why leaves change color and fall off.
Mm-hmm.They have to hibernate.
Like bears, they gotta store their energy.
Yeah.Gotta save it up for the spring.
To then regrow those same leaves.Of course, the primary and most obvious purpose of a plant's root system is absorbing water and nutrients from the soil.Sure.
So the part of the roots that actually pull in water and nutrients are countless teeny little root hairs that grow all along the outer cell wall of the root.And as the name implies, these are teeny tiny little hair-like growths.
The water then is sucked up by these hairs and passes through the cortex, which is the main tissue of the root.The cortex is the part of the root often used for energy storage by plants in the form of starches.
But the cortex also otherwise serves to separate the outer cell wall of the root from the inner cell wall.These outer and inner cell walls are called the epidermis and endodermis, respectively.
Epi meaning outer, endo meaning inner, dermis meaning skin.So outer skin, inner skin.
Oh yeah, there's, I apologize now, there's gonna be a few of those.
I think it's interesting, too, because we normally think of cortex, I think, as like an inner or even like a spiral to some extent.Yeah.
So the fact that what is essentially like a middle wall of a cell structure is also called that, I think, is interesting.
Yes.And it's kind of an intermediary layer where it is not the true center, but you could think of it as the middle if you bisected the root or cut it in half.
You could think of it as being in the middle because it's between the outside and the true inside.
Anywho, with the epidermis acting as a kind of skin between the outside world and the insides of the root itself, and the endodermis acting as a secondary skin between the cortex and the plant's vascular system.
Yes, we're finally getting to the vascular part of vascular plants.
Just as we have cardiovascular systems, where our heart pumps blood through our bodies using arteries and veins, trees, grass, flowers, and other vascular plants have a vascular system that works passively to move water and nutrients throughout its body instead of veins and arteries.
Plants have something called xylem and phloem.
So xylem is the part of the vascular system at the center of the root that transports water and water-soluble nutrients, or nutrients that have been dissolved in the water, right, minerals and whatnot, up from the roots into the rest of the tree or plant.
So extending to every branch, twig, leaf, and flower.So you can kind of think of the trunk of the tree as kind of this giant bundle of teeny tiny straws moving water up the body of the tree.
The way that trees actually do this, and all plants really with vascular systems, is through something called capillary action. Capillary action is this fascinating relationship between adhesion and cohesion in water molecules.So adhesion.
Stuff sticks together, right?
Cohesion, stuff that is the same, likes to stick to itself.
So water has adhesive forces when in really tiny little spaces where it will stick to something, right?If you touch a paper towel to water, the water pretty quickly sucks itself up into the paper towel.
Water likes sticking to other things, but water also likes to stick to itself.In certain circumstances, with teeny tiny little pores or holes, you get water pulling itself up.
So if you stick a paper towel, like lengthwise, hold it from the top and dip it gently into a little puddle of water, right?
You'll see- The water kind of crawls up it, yeah.
Yeah, it crawls up because that paper towel has a bunch of spongy little pores all throughout its surface that the water sticks to and the adhesive forces pull the water up into the next pocket while the cohesive forces of the water
And it is limited somewhat in its strength.
So if you stick a typical smoothie straw or straw from a fast food place into a cup of water, you're not going to see much of this.You might notice a teeny little bit of it with a clear straw, like a U-shaped dip.
in the water level of a straw, that is a very weak but present form of that, of those forces.
So capillary action is those forces at work pulling the water up through the body of a plant.
Now the vascular system also transports energy from the leaves to the roots.
Okay, so is this kind of like an expressway that goes in two different directions?
Yes, that's a great way to think of it.
Yes.The energy gained during photosynthesis in the leaves is used to turn the carbon dioxide breathed by a plant into complex carbohydrates or sugars.Right.
That are then transported from the leaves downward through the plant through what is called the phloem.
Okay, so xylem goes up, phloem goes down.
More or less, yes.Cool. It's the other main vascular tissue that sits right alongside the xylem throughout the tree or throughout a given plant.
Together they then act as the veins and arteries.
Plant roots also typically grow both downward and outward, right?As much as possible to collect the water and nutrients in as much of the soil as it can reach as possible.
Well, at the tips of the roots, they generally have what is called a root cap, which is just this hard little shell that protects the tip of the root as it grows downward.
So the root cap actually needs to be partially regrown constantly as it's damaged by being pushed into the soil, while the actual growth of the root happens just behind the root cap and pushes it forward.So as a root grows, it's kind of like
Fingernails?Yeah.That's what first came to mind for me.Sure.
Because the root cap gets pushed by the progress of the cells dividing behind it. and the cells dividing behind it are actually then growing the rest of the root as it moves along.
Now as far as the growth patterns of the roots, many people, I would expect, would be familiar with the concept of a tap root, right?Which is the sort of leader root that delves downward and could be thought of as
analogous to the main trunk, so to speak, of the underground portion of some plants.Not all plants have taproots, but those that do will often have secondary roots growing sideways off of the taproot at various depths.
Right.I feel like that's the diagram image we were always shown in like grammar school.
Yeah, one of the most common ones is of those type of taproot systems, of that one leader delving downward and a bunch of little guys branching secondarily off to the sides.It may be surprising though to learn that most trees don't have tap roots.
Rather, I should say, most trees outgrow them after a time.So plenty of them have them as saplings.But once they are a little more established, then they grow lateral roots that often spread sideways.
And those sometimes send deeper shoots underground as well.So you end up with a lot of branching downward in the root system from a main lateral sideways growth pattern.
So it's kind of like a family tree.
Because you have all the layers of the great, great, great grandparents.Then that's very wide normally, the family tree image.And then as the generations come after that, it starts to typically get more narrow.Yeah.Until you hit you, usually.
That's not a bad way to think of it.
There are, of course, exceptions to this, but root growth patterns are often at least a little unpredictable, right?Because roots typically grow opportunistically.
I know a lot of people often bring up fractals and the golden ratio, particularly in the nodes and branching patterns of plants. that is more applicable to their stems growing above ground.
The roots generally are more unpredictable and will just grow wherever there is an opportunity or space.So less present underground in terms of fractals and golden ratio.
Well, and you think about like if you plant a bush or a tree in your backyard or something and you plant it too close to your fence or too close to your house or too close to another established older tree, it's going to have a hard time growing well because a lot of that space around it has been taken up by the root system of the other plants or the concrete of your fence or your house or whatever.
Right. I will say oaks are actually a great example of lateral root systems because most oaks develop a majority of their main root structure as lateral roots after the taproot has allowed them to establish themselves sufficiently.
And these lateral sideways growing roots usually are no more than maybe four feet below the ground.
In my yard it's even less.We live on a hill.The soil erosion is pretty significant over the roots of our oak trees.We're working on it.
But yeah, that's not too unexpected with oaks.Though it is, it does feel weird, right?Because you think of that classic image of a tree above ground and then an almost identical system below.
Like the Celtic knot tree, like tree of life thing.
Exactly.That is a fantastic artistic depiction.I love it. It usually doesn't pan out that way for most plants.Sure.
And oaks are a great example of that because their roots, again, typically no more than four feet below the ground and often spread up to twice as far away from the tree as the edges of their above ground branches.
I guess that kind of makes sense because you have to think that I mean trees in general are essentially top-heavy and you need a solid wide base to handle the weight distribution and like truly anchor something that's that tall and that heavy and that top-heavy in particular and
Right.It's just amusing to think that it doesn't actually need to go that deep to get the same level of anchorage.You just need to spread out wide enough.
Now what about mangroves?
You jumped ahead literally two sentences.
So for mangroves, we're going to talk about aerial roots.Aerial roots, I really enjoy the visual of them.
But they're generally roots that have actually begun growing above ground and then delve underground.Corn is another good example of this.
I feel like having grown up in the Midwest, I should have known that.
Probably but you also it's not like we grew up in cornfields.This is true.We're not farm Midwest were suburban Midwest, right?
So yeah, but still for all the talking everybody does about farmland and soy and corn and wheat and whatever in Like our education system at times you would think they would have mentioned this about corn sure, but
I feel like most of the time in the Midwest, if we're learning about corn, we're learning about it from an agricultural perspective and less from a botanical and biological perspective.That's true.So aerial roots.
unfortunately fall by the wayside, even though they're really cool.And with corn, they're typically referred to as prop roots because they prop up the corn.
They grow in a short little ring, roughly, around the base and just above the ground, and then dig themselves down, almost like extra little fingers reaching down and just grabbing the earth and soil.
However, mangrove trees, which tend to grow in coastal or otherwise brackish, salty water in tropical and subtropical regions, mangrove forests, they grow long tangles of what are called stilt roots that, as the name implies, they act as stilts to hold most of the body of the tree above the waterline for high tide.
And actually those roots act to slow down fast moving water pretty effectively.So sometimes you get mangrove swamps.
Right.Down near the Everglades or like New Orleans or places like that.Right.Yeah.
Where you get the fast moving water slowing down as it tries to pass through this mess of roots.Right.
Which actually, because it slows down the water, a lot of nutrient-rich material falls out of water, like falls out of suspension, and ends up then enriching the soil around the mangrove trees.
So they encourage their own growth by means of, yep, the water's going to drop off a lot of nutrients as it passes by here, and helps just control the flow of the tides in those areas.
Many plants that do keep their tap roots do end up turning them into a centralized energy storage system.Like I mentioned earlier with carrots, those are called root tubers usually, which also include radishes and beets.Fun side note, potatoes?
So they're tubers, but they're not roots.Huh.Potatoes are actually stems. and they grow on a special stem underground called a stolon, but they're not actually themselves roots.Sweet potatoes are root tubers though.
Yes.So I don't, it amuses me that we call sweet potatoes, potatoes, and yet they're not technically the same thing as potatoes because potatoes aren't roots, but sweet potatoes are.
Yeah.It's a whole thing. Then, of course, there are other plants which don't have thick branching roots, but instead have what are called fibrous or adventitious root systems.
These tend to grow thin, long tendrils of roots that interweave and may spread wide and deep, but focus more on quantity of roots than thickness or individual roots.And they grow into this web-like mat of roots.
I feel like when you pull up crabgrass and things like that, that's kind of what it feels like the systems are.
Yeah, grass is a great example of fibrous or adventitious root systems.Onions, wheat, rosemary also have that similar structure of just these little web-like hair fingers of fruits going everywhere.
Okay, so that's kind of our quick overview on roots for plants.
Maybe not as quick as I would have liked, but so be it.We're going to shift quickly to fungi, which God's fungi are weird.
They are.We love them so much in this house.
So I also want to clarify that I'm saying fungi or fungi interchangeably.I think both pronunciations are fine.
But I'm saying fungi instead of mushrooms because mushrooms are actually
They are the fruiting body of a fungus.
So a given fungus might have mushrooms.Some fungi don't necessarily have mushrooms in the way that we would think of them.And the mushroom itself is not the entire body of the fungus.
So kind of like the buds or like the flower of a tree.You wouldn't say that a lilac bush is the flower.
So it's a similar... And apple is not the hell apple tree.
Right.Yeah.Right.So there was a time when fungi were thought to be the strange category of plant, like this weird offshoot. But as people learned more and more about fungi, it became very clear that they are very different.
This confusion was, and for many people honestly still is, mostly due to how some mushrooms look like a little plant stem, right?Growing up from something that kind of looks like roots.Yeah.
And since they have rigid cell walls and are immobile like plants.
That's good enough for most people to say, hey, looks like a plant.It doesn't walk like a plant. Great. The way we classify living things today was largely based on the writings of biologist Carl Linnaeus, who set forth the idea of three kingdoms.
Plants, animals, minerals.
OK, because I remember that from grammar school science, I think.
Yes.Since minerals are not living things, it has long since been dropped from this classification system.But the general method of describing things based on shared traits and ancestry has stuck around.
Also, fun fact, I think plant-animal-mineral, I think that is the origin of, in the game, 20 questions.One of the classic beginner questions is, is this a plant, animal, or mineral?
Yeah.Now, regarding the separation of plants and fungi, while there were rumblings and general discussions among botanists and other biologists for a while, decades at least,
about whether or not fungi were their own kingdom, the first article that I could find that is typically credited with majorly revising this framework and thus treating fungi as their own kingdom was an article titled, Are Fungi Plants?
Written by George Willard Martin in 1955.
That's more recent than I would have suspected.
And again, just because this is the guy who gets credited with this does not mean that he is by
For all anybody knows, it was a woman.
Yeah, he's just the author who gets cited most often as shifting the viewpoint in the public eye, at least.George argued that since fungi do not produce energy through photosynthesis, they cannot be considered plants.
They also fulfill a different ecological niche than plants. So while plants photosynthesize and thus produce energy from sunlight, fungi receive their energy by absorbing other living or recently living things.So they often act as decomposers.
So you have plants as producers, animals as consumers, and then fungi as decomposers.
Yes.A distinct role in the ecology of our world.
Right.So as fungi help decompose things, which I think, you know, like when you walk in a forest, right, during the fall or whatever, a lot of what you smell is actually rotting leaves and bark and trees and stuff like that, right?Right.
And that's happening in part because of the fungi.And then does that release some of the CO2 that plants breathe?
I would have to double check on that, but I believe so.
Right, because I know with plants the main force of energy production is the photosynthesis.
Right, right.But they do breathe that CO2.Yes, I'd have to double check that to be, to say for certain. So this does actually mean that fungi acquire nutrients more similarly to animals than to plants.
Oh, right, because they eat stuff, essentially.They're eating the dead things to make them more dead.
Yeah, they eat things to get the energy from them.Yeah.And that's actually in biology referred to as being heterotrophic. which means specifically that the source of their nutrients is consuming other living things or recently living.
Hetero meaning other and trofe meaning nourishment.While plants are autotrofes.They are self-nourishing from sunlight, of course, and water, minerals, whatnot.
Right, but the processes are happening internally.
Yeah, the biological processes are creating rather than consuming.
Additionally, I mentioned a moment ago that fungi can't produce energy from sunlight because they don't have chloroplasts, which are the organelles responsible in plant cells for photosynthesis.
The little green dudes, right?
Exactly.That's why plants are green, are those little chloroplasts.They're responsible for photosynthesis in plant cells.Fungal cells don't have those, so they can't do it.
Another separation I wanted to mention between plants and fungi is one that I've heard broadly bandied about here and there, but I never really hear explained fully, but I think it's really interesting, so I want to mention it.
So it's often said that fungi and animals are more closely related than fungi and plants.
And when biologists say that, there is a common ancestor that all fungi and animals are both descended from that was already distinct from plants when it evolved.
So plants began evolving and then a different branch off of organisms separately and independently split into animals and fungi.
The animal kingdom and fungal kingdom are sometimes collectively classified as a unified clade.Again, grouping.
called the opisthokonta clade.
It's quite a word.The word opisthokonta coming from the Greek words opisthios, meaning rear or posterior, and kontos, meaning pole or flagellum.
So flagellum are basically just little hair-like tails that provide mobility to teeny tiny things.And what comes to mind first?Uh-huh.Yep.Yep.Sperm.
animal sperm and some fungal spores have a singular rear tail that aid their mobility and allow them to move around.
Makes me think of tadpoles too.
Yeah, that is a shared trait that began in the early stages of animal and fungal evolution.
And is shared between them.Now, I say that some fungal spores have this, because currently most fungi have actually lost that trait.They've evolved away from it for the most part.
Some still have it, but most have evolved away from it for one reason or another.But in terms of genetic heritage and evolutionary ancestry, they used to.So animal sperm have kept the flagellum while fungi have mostly abandoned it.
But I love that little connection.
Because that is such a weird, of all the ways to connect.Sure.These organisms, human sperm is similar to fungal spores.You're welcome for that imagery.
Okay, so now we finally get around to what the hell I mean when I say that fungi don't actually have roots, but they have something that looks root-like.
Fungi actually have what is called mycelium.
So other than being a rare and fun dirt block variant in Minecraft, Mycelium are vaguely similar to plant roots in visual appearance.Yeah.
And they are more or less the fungal equivalent, but they're not structurally the same and they operate entirely differently.So they can't really be called roots because they serve a similar purpose but function very differently.
Plant roots transport water and nutrients throughout a plant by means of the xylem, while mycelium are a collection of extremely fine, hair-like branching filaments called hyphae, which also transport
enzymes and nutrients throughout a fungus, a single hyphae, hyphae just being like a single node of mycelium, typically has a diameter of four to six microns.
Keep in mind folks that a single micron is one thousandth of a millimeter.
Yeah, so like not even really all that capable of visualizing that.
No, no, it's too tiny for most people to visualize.Yeah.
All right, so these hyphae are really small then.
Oh yeah, these hyphae are tiny.Typically only one or a few cells wide, and they're surrounded by this tube-shaped cell wall.
So similar to plants having a cell wall, hyphae and other fungal cells have a cell wall as well. Many hyphae together form mycelium.
And this then brings me back to how fungi get their nutrients, right?So they typically do gather nutrients through their mycelium.But remember that I mentioned that fungi, like us, are heterotrophs.They consume.Right.
Fungi have two kind of three main methods of consumption.
There are saprotrophs, which are fungi that eat dead things. They break down non-living organic matter by releasing digestive enzymes? through their mycelium that then deconstruct that organic matter into its base components.
So the ones we see on dead tree trunks release their equivalent of stomach acid to eat the dead tree trunk.
Yeah.Cool.It's like a fungi regurgitating its stomach acid onto a meal before consuming the meal.
We should maybe put a warning at the beginning of this episode to not watch it right before or during a meal.
Yes, yes.Because thinking about a fungus baby birding itself, maybe not the most pleasant imagery.
But again, there's another similarity between animals and fungi, right?
Yeah.And it's not the same thing as stomach acids, but it is their equivalent more or less.But they release these through their mycelium into whatever they're latched onto or weaving through.This then breaks down proteins into their base amino acids.
Starch is broken down into less complex sugars and other enzymes.And cellulose is broken down into glucose.
So these are then reabsorbed into the fungus and used as its own raw materials.
So then do plants not break down?Do they not create like enzymes and stuff like that?
They have some enzymes they create and use throughout their body, but they aren't typically releasing anything, at least as far as I'm aware.
Or using them to create energy for themselves the way
Right, not in this way.Okay.Yeah.And then fungi also gather energy through symbiosis.
Yes.Well, they can be parasitic or mutualistic.
So mutualistic is a version of symbiosis where it's not harmful to the other organism.Right?We're familiar with parasites and parasitic relationships of one thing leeching all the energy out of something else.Right.
Mutualism is they both get something out of it, and they're not really harming one another.
Like our microbiome in our gut.
Exactly.Yeah, those are mutualistic, symbiotic bacterial organisms in our gut.This then leads me, finally, oh, one of my favorite examples of... We have reached the root cap.Yes. Yeah, more or less.
One of my favorite examples of mutualistic behaviors in fungi is also a major bridge between fungi and plants.
This is part of where the drama comes in later.
I'm going to present it first and then we'll discuss some of the caveats later.This connection between plants and fungi is created when a fungus' hyphae grow into the roots of a plant.
This is pretty common among both mutualistic and parasitic
Symbiosis fungi?Yeah.Okay.
They'll reach into other living things with their mycelium.But in this case, this plant-bonded fungus then becomes known as mycorrhiza.
Independently, mutualistic mycorrhiza can provide additional means through which the plants they connect to can receive nutrients like nitrogen, phosphorus, and sulfur.
They kind of help pass along some of their unneeded nutrients into the plant and take some extras from the plant that it might not need.
So, multiple plants may then become connected to mycelium in this way and form what is then called a mycorrhizal network.Or sometimes you'll see it referred to as a common mycorrhizal network, CMN.Same thing.
There is a 1997 Nature Journal article entitled, Net Transfer of Carbon Between Ectomycorrhizal Tree Species in the Field.
This was one of the early papers which discussed study results indicating that mycorrhizal networks were acting as a bridge between various trees and supplying nutrients from trees with excess resources to trees within their network that were in need of either phosphorus, carbon, nitrogen,
Oh, okay, yeah.I've heard vaguely of this.This is like part of how people think that trees talk to each other and help each other survive and stuff like that.
Yes, exactly.And what is sometimes described as like the wood wide web, which is a really fun way of- Describing all of this.A fun moniker.
These fungi can then create an interconnected web of plants that work to keep each other alive because they all benefit from this connection.
The lead author of that paper, Suzanne W. Simard, a forest ecologist from the University of British Columbia, has since contributed to several similar papers and studies which further investigated how fungi may contribute to the overall health of a forest through this type of mutualistic symbiosis.
wherein the fungus takes a little tax, so to speak, a little toll of energy and nutrients, largely sugar and carbon, usually, in exchange for sharing some of the nutrients between trees to which it has connected itself.
Right.So they're like the hub.
Right.This little connection between various plants, keeping them all as healthy as it can while feeding itself.
This would then allow other young saplings growing in areas that are otherwise potentially too shady for them to perform adequate photosynthesis on their own to still grow over time until they can eventually reach the canopy of the forest and sustain themselves with their own energy production.
Or maybe a neighbor falls down and then a patch of sunlight is available.Either way, the idea is this would potentially help some of those young saplings
Yes, exactly. This has then also led to discussions in the community of what are colloquially referred to by the media as mother trees.
These so-called mother trees are also then called hub trees since they act as the plant central hub of their mycorrhizal network, kind of being the older, taller, more well-established tree that then have larger, more well-developed root systems capable of gathering more nutrients from a wider area
And then the mycorrhizal network distributes that energy, any excess, to the younger trees nearby.
This network of fungi that allows the older trees to functionally take care of and nurture the growing trees.Yeah.
And as you mentioned earlier, the communication element, there is along with that often talk of plants communicating various dangers or hazards.If like one plant is being eaten,
that information being shared via the passage of enzymes and nutrients from one tree to another.Like what tree might need more is an indicator of, oh, this tree maybe is suffering from this type of pest or something or other.However,
I will say that this has often taken a few steps potentially too far in most articles, and even how I've presented it so far is probably a little further than it actually is, especially when discussed Outside the field, right?We're not experts.
I'm no botanist.I'm no mycologist, right?And I want to be careful in talking about this that I don't Necessarily go too far into speculation and untested a hypothesis without giving this disclaimer, right, right It's a really romantic idea.
Oh, absolutely clearly caught the imagination of a lot of people, right?
Yeah, because we have a tendency as humans to personify natural phenomena and apply our own human biases to it.
So these connections are often spoken of in a way that evokes this imagery of a massive connected network of trees and fungi spanning miles of territory in a forest and is described as if the trees are detecting distress in their neighbors by means of the fungi sending nutrients in response.
But that is probably way too humanized an idea of these plants. and fungi.There are plenty of researchers that are more than a little hesitant to fully embrace that kind of description, especially in the large scale of a full forest.
Justine Karst, Melanie Jones, and Jason Hoeksema, again, hope I'm pronouncing those names correctly, published a paper in the 2023 edition of Nature Ecology and Evolution.Now, this paper, just the title.
Oh, good.It's another one, isn't it?
Yes.Great.The title already gives A pretty good idea, but we'll break it down in a second.Positive citation bias and over-interpreted results lead to misinformation on common mycorrhizal networks in forests. That was the title.
I'm pretty sure that's a sentence, not a title.
Yes.It can be both.It can be both.
This paper more or less points out that common mycorrhizal networks are not necessarily as grand or widespread as most people often like to portray, and the idea of mother trees being preferential in where they send excess nutrients
isn't broadly supported by evidence and may in fact be overrepresented by a couple of studies being oversighted.They are referred to too often by countless sources, countless media outlets, countless other papers just referencing these papers
I mean, it kind of makes sense too because, yeah, I think even if there are this idea of mother trees that are sending out extra nutrients, I can totally see how the personification of this would lead to, yes, all the little babies and, you know, whatever.
But in reality, I feel like maybe it's more like you tapped a water system, you know, aqueducts or whatever, where the nutrients are just free-flowing down the pathways to whatever is on the other end of the pathways.
It's not, we're specifically feeding one thing or the other.
Right.And that's, that's like the first point of contention of, well, all right, the media likes to romanticize things a little too much.So, and that can be dangerous in people's perceptions of these ideas.
The other issue that this paper brings up is a lot of these studies looking at the transfer of nutrients from mother trees to saplings are often too small or narrow in scope and scale.
So they're looking often at potted plants or like small plots of land and not necessarily taking into account the full large scale of the forest.
So, but so many people have cited the research that make these claims and have subsequently speculated on that research.And people have a bias towards this personification, which means that we end up muddying the waters.
And basically this paper argues that the research currently done
just isn't conclusive enough to be used for definitive changes to forestry and conservation strategies, and that more research needs to be done to better understand the mycorrhizal networks and the relationships within and between them.
Right.And like larger forest scale studies and things like that.
Right.Yeah.Not necessarily discounting or discrediting the previous authors, but just pointing out that, hey, we need to do more research before we make huge broad claims.
But Suzanne Simard, the author I mentioned earlier, who has done a bunch of the research that supports much of the positive and large-scale view of mycorrhizal networks, has said that she stands by her research and that a focus of her research is to avoid taking a reductionist view of complex systems.
And there's definitely something to be said for everything that's going on here.
Because personally, I agree wholeheartedly insofar as reducing complex systems such as an entire ecosystem to individual parts can be very dangerous and potentially lead to a failure to fully understand that system.
And that's part of what Suzanne Simard is arguing for, right?Understanding how a forest as a whole works together and works as a biome rather than looking at, well, this tree behaves in this way and this bird behaves in that way.Sure.
But it's also, I also really appreciate any study that looks at and compares multiple other studies and points out flaws in the community's understanding or widespread acceptance of a given piece of information.
Well, because it gives you new areas to focus on and research and discuss.
And again, never take anything at face value.And a ton of science is, hey, somebody made some claim.They've done some research.
A ton of science is just looking up and redoing other people's research to make sure that it's valid and repeatable and verifiable.
because it may well be true that on the large scale, these networks are as beneficial and impressive as they may seem, but it's only really been shown to work that way in fairly small networks and in relatively tightly controlled studies that don't always control for every possibility that they should.
At least it has been pointed out, well, you could have controlled for this and that better, but at the very least, it's also dangerous to get carried away with limited information
because yes, the information may be promising, but promising is not the same thing as definitive.This area of research and mycology in general is still fairly young as far as scientific fields of study go.
As we learn more and more about fungi, I do hope that more studies will be done specifically on this topic because I find it so fascinating.
Yes.And again, at the very least, it's a very fun idea that if it works at least neutrally on the small scale, great.Very cool.Very fun.Very interesting.
Yeah.It's still a new part of ecology and botany and biome study that, you know, we didn't have a clear understanding of or even knew existed, however many decades ago, you know.
So that, I think, wraps up my first chunk here on plant roots, mycelium, a fun little connection between them, some of the differences.
Now that we've covered the main information on these systems, we're going to take a quick break.
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The lights are flashing, folks.Intermission's over.Let's get back to the show. All right, welcome back to our more discussion-oriented portion of the episode.Cara, what do you have for me?
Well, I have a few questions.
One of the ones that came up near the beginning was you had mentioned clades and you did a great job defining that, but I'm wondering how are clades related to like kingdoms and genus and that whole structure that we learned in biology sophomore year of high school?
Right.So those ranks, domain, kingdom, phylum, class, order, family, genus, species.Sure.
Those eight major taxonomic ranks are, they're the major rankings by which the tree of life is broken up when looking at it evolutionarily and through this lens of analyzing how species have evolved from ancestor to descendant, right?
Domain, kingdom, phylum, all those are the large breakdowns, like some of the big milestones, so to speak.And clades are a more general, in terms of what you group as a clade, because a genus, which contains multiple species, that is a clade.
Different genuses are clades, families are clades, orders are clades, but
you could also make a clade like a pisticons or... So clades can kind of be used when you might actually be mixing some of those ranking systems or species from different ranks together into one group because they have some commonalities that are kind of outside the traditional ranking structure.
they're like more specific because like there's not, there are not only eight steps of evolutionary growth from the beginning of life to any species that exists.
There are what are generally considered eight major classification like regions, so to speak, on the tree of life.But Anywhere in between, there's a ton of other branching that occurs.So a clade is still all descended from one common ancestor.
So taxonomic rank are these big building blocks of understanding the tree of life in more of a top-down approach, whereas clades are more specifically a grouping based on a singular shared trait and common ancestor.
But again, as we discussed with animals and fungi, a lot of fungi no longer have those flagellums.That shared trait has evolved away.
Some still have them, not all, but they still are one shared clade because of that common ancestor and that trait that was passed down.
So would whales and snakes be in a clade together because they both have the vestibular hip bones?
That is more in the realm of an example of convergent evolution.So things that happen similarly, but are not necessarily related to each other genetically.So flight, flight is a great example of convergent evolution.
It's happened four separate times throughout Earth's history.
Isn't it like bats developed it separately from birds?Yes.Separately from insects kind of a thing?
Yes.And the fourth one being pterosaurs. Pterosaur, pterodactyls.Yes, yes, yes.So pterodactyls are a type of pterosaur.
Those creatures developed flight separately from insects, developed flight separately from birds, developed flight separately from bats.They are not all descended from one common ancestor that learned to fly.
Rather, they all separately were fulfilling some ecological niche and developed this trait as a means of survival. So likewise, snakes and whales, yeah, they lost some extra limbs or their limbs changed, but that isn't because of a shared ancestor.
Actually, funnily enough, trees are another example of convergent evolution.Trees are not a singular clade of organism. tree is just a description that we apply more linguistically and more, more agriculturally than botanically, I would say.
Where any sufficiently woody, like hard woody plant that grows tall and has that kind of, that structure that comes to mind when you think of a tree, Any plant that is sufficiently close to that tends to get called a tree.But bamboo is grass.
Palm trees, I believe, are grasses.Let me double check that.Yes, palm trees are actually a type of grass.They just are sufficiently woody enough.
And tall in their appearance that, yeah, we call them trees. But yeah, tree is not actually a descriptive term of a clade.
Because they're not, like yes, all trees are descended from a common ancestor, but so are a ton of other things that are not trees.And we would never think of as trees, are still descended from that same common ancestor.
Trees themselves are not all like one genetic group.
Right.So one of the other things that I thought maybe we could dive into just a little bit is this idea of fractals because we mentioned it briefly.I love fractals.I'm obsessed with them.But when we had mentioned fractals it was
how branch systems are often fractal in like mathematical patterning and design, but root systems aren't typically.So let's like maybe define fractals for our friends and talk about that a little bit more.
Yes.So, fractals, it is a self-same pattern that repeats.In mathematics, a fractal can repeat indefinitely.Obviously, in biology, it's not going to present quite the same way.
The term fractal does still get used to describe repeating patterns in a plant's biology or appearance.And when I say self-similar, I mean that it is a repeating pattern that shows up over and over.
If you look at a true mathematical fractal, at any point along that fractal, no matter how much you zoom in, it is the same pattern repeating over and over and over and growing outward.
The main branch comes off of the tree and then the two branches that come off of that main branch are similar in pattern to that first branch and the little branches that come off of those two branches are all in general shape and look and structure similar to each other.
Yes, but also specifically with plants and their branching growth patterns, we get more into the Fibonacci sequence and the Fibonacci curve or the golden spiral.
The golden spiral being one of the classic visualizations of the Fibonacci sequence, which the Fibonacci sequence, every number in the sequence is the previous two numbers added together.So you add one to zero, you get one again.
You add 1 and 1, you get 2.2 and 1, 3.3 and 2, 5.5 and 3, 8.So on and so forth forever.
So that pattern, when visualized, produces this spiral image.
Yeah, it's kind of like a, looks like a nautilus.
Yeah, the nautilus shell is a great example of the Fibonacci curve or golden spiral appearing in biology.Right?And likewise, this This sequence, I referenced the golden ratio earlier.
The golden ratio is specifically the ratio between two numbers in sequence.Okay.So like the ratio between 3 and 5 is 1.6 repeating.Okay.The ratio between 5 and 8, 1.6.
The ratio between 8 and 13, 1.625. The further down the sequence you go, by the time you get to 144 and 233, the ratio between those is 1.61805, repeating.
That number, 1.618, and there's more digits to it, but that is, in many plants, the pattern of branch growth follows that ratio.Where you could say from stem to tip, the rate at which new branches develop is approximately equal to that ratio.
Approximately this many branches will grow out of each branch per unit distance in many plants that we see.There is also a lot more of the Fibonacci curve and the golden spiral and these other fractals, right?
These repeating patterns in flower petals, right?And leaf growth patterns.
It's very noticeable in flowering plants that have a lot of petals repeating right on top of each other, where you see kind of the spiral form of the flower petals, one right under the other.
Like the roses and stuff.
Yes.And just slightly offset.And part of that is just the efficiency of producing those petals or those branches, those leaves, at regular intervals.
So the least amount of energy you can expend while gaining the most back from it, for a lot of plant growth patterns, ends up being approximately the golden ratio.
Yeah, it's one of those things where like the crossover of math and beauty in different forms, right?Like we see math in the golden ratio and therefore in trees and in river systems and in petals on the flowers.We also see math in music.
It's a really interesting, I think, common theme in things that humanity has deemed beautiful in some form or another.You can often find mathematical ratios.I just think it's really cool.
Oh yeah.And of course, I'm kind of a broad overview of this idea.
I'm sure- We could probably do a whole episode just on fractals, but- Oh yeah, and I'm sure any mathematicians who are listening right now are pulling out their hair going, no, no, you're not, that's not, you need to be more specific, which, fair, completely fair.
I am glossing over a bunch here, being very general.And botanists, biologists, mathematicians, I'm trying, but I'm also trying to be very, I'm not trying to get too lost in the weeds, so to speak.
But also, do feel free to correct us if this is your field and your expertise.Feel free to comment and leave more specifics because I certainly don't have the time or knowledge to give too deep a dive into just fractals and fractals in nature.
There is a really good documentary on it.I don't remember where I saw it, but I'm pretty sure if you search fractals documentary, it will show up.It's very approachable for how it explains it.
And it goes into the history of who kind of really discovered them and created the mathematical formula for it and how they use it to like measure and properly map the distances of shorelines.It's fascinating.
Oh god, the shoreline problem.
Yes, that will get very off topic, so we're not going to go into those.But it does exist if anybody wants to delve into it a little bit more on their own.
You may have also heard the golden ratio referred to as the divine proportion or the extreme and mean ratio.
Anybody who's had to go to an art history class, you've seen it.They've probably beat you over the head with it.
But no, so that's really cool that, again, that intersection of math and beauty and math and nature, plants and all that.
Right, it's a nice mathematical description of what we see and intuit, what we understand innately, but don't always necessarily think about.
Plus it's a couple of autistics, we really love anything that has to do with patterns.
The last thing that really came up for me while we were talking about this that I think would be good to touch on a little bit more, we'd mentioned roots and how combined with soil they are an anti-erosion system.
which, again, grew up in the Midwest, that might bring something very specific to mind, which is the Dust Bowl, where we had extreme erosion from wind in a drought that essentially decimated the agriculture throughout the Midwest.
And I think it was Roosevelt Ended up starting a program as he was want to do right?
Well, cuz this was the like the 1930s, correct?
Yeah era, which of course, you know depression era did not help know that our agricultural area was you know experiencing a drought and not being able to grow anything because our soil was sucky and
Not an insignificant contributor.
No.No.At all.If you've ever heard of potato sack dresses, that's where this came from.Wheat and potato companies began to print designs on their potato and wheat sacks so that mothers could use them to make dresses.
But the way that the US government helped mitigate this whole devastation was to begin planting trees.
So when you see those kind of classic overhead images of the Midwest and you see all these parcels of land that are square shaped and that seem to be ringed by trees,
A lot of those sections, especially those with trees that are old enough to really be visible from high up or whatever, likely were planted during this period of trying to mitigate the effects of the Dust Bowl and bring trees and root systems back into the soil to hold it to the earth, literally.
Right, because especially in large prairie land where there isn't much tree and there's a lot of... We'd gotten rid of all of the natural grasses whose roots had kept the soil in the ground and, you know, healthy.
And farmland only does so much of that, especially when the surrounding land is also completely deforested, defoliated.
Right.Because you have to imagine you're taking those root systems out when you harvest the plants.
So yeah, I just think the science of it and the basic understanding of roots and erosion has been so important to American history and agriculture.
Oh yeah, and the consequences of not appropriately accounting for erosive forces sooner.Yeah.
Yep.And you see it along, you know, the banks of the Mississippi too, where people have pulled up grasses and trees and all of that along the banks and then the banks flood because there's nothing keeping the soil in place anymore.
So then the banks get destroyed.
And pull way too much soil away from the banks and the river ends up wider than it should be and then shallower.So it's moving more slowly.
It just goes to show, I think, how much planting trees and planting native foliage are so important.We will probably at some point get into the whole climate change issue.
But even when you don't look at climate change as a whole in terms of carbon dioxide or the atmosphere or warming temperatures or whatever, when you even just look at things like erosion on riverbanks and erosion in agricultural areas, again, it comes back to just plant more trees.
Just plant more grass.Real, not native grasses.
Right, native grasses, not invasive species.Then you end up with things like kudzu, the vine that ate the South.
Yeah.Just having an increase of native life in a given area is weirdly better for the entire ecological zone.Strange.Yeah.Who would have thunk?I know, weird.
Yeah, but it really is, it's a very common theme, not just in the United States, but globally, of truly plant more natural plants back where you took them up from, and you might see some significant positive consequences.
So yeah, I think it's really interesting.I'm excited.You know, I think we mentioned in our intro, this is part one.
So we are going to be getting into more specifics with Josh at the helm later on of specific examples of like wonky and cool root systems and further into things like fungi and mycelium.
Yes.And that's not to say that I won't soon have episodes on the life cycles of stars.Oh, I'm getting there.
We're getting there.We're getting there.
But I definitely have a few early on here that are about various plants and fungi.We'll branch out from there.
Good.We got another one in.
Hey, we're close to the end.I gotta squeeze in one more.We do.We do.
But yeah, I think this has been really interesting.And I know I learned a lot.
It's very fun.And I'm glad, because if I make this too dense and unapproachable, I've done something wrong.And I hope I've made today's episode relatively approachable in information.If not, let me know in the comments.And I'm sorry in advance.
And with that, I know we always say this in our outro, but I think it's important to reiterate throughout the episodes is there are graphs and images as well as our resources and research available on our website under our episodes tab.
So some of this stuff that Josh explained, like the inner structures of roots and whatever, if you're a visual learner like me,
There are things to go look at that might help some of this stick a little bit more, or if you look at that tandem while you're listening to this, can just be a useful little extra research for you.Yeah.Yeah.Yeah.
All right.I think that about does it, unless you have anything else.
No, that was everything I had.
That's a wrap on episode two, Roots.If you'd like to delve further into this topic, our research and sources and related images are posted on our website, www.hyperfixation-investigations.com.
Again, that is www.hyperfixation-investigations.com under the episodes tab.And we thank you so much for listening.
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