Roger: 0:02

Talking Trees with Lily and Jad. Welcome to today's episode. Get ready to dive into the fascinating world of plant growth regulators, also known as phytohormones. From auxins to cytokinins and beyond, we'll uncover how these regulators influence vascular tissue production and whether the cambium itself is genetically programmed for this essential function. Stay tuned as we break down the science behind the growth regulators that drive the plant world.

Jad: 0:35

Welcome back everyone for another deep dive. This time we're tackling plant hormones and growth regulators.

Lilly: 0:41

Tiny but mighty messengers that pretty much run the show when it comes to trees.

Jad: 0:47

Especially relevant for all of you arborists out there.

Lilly: 0:50

Absolutely.

Jad: 0:50

I've got a couple of new research papers here.

Lilly: 0:52

Oh cool.

Jad: 0:53

Really digging into how those hormones affect everything Growth, development, even how trees handle stress. Fascinating stuff, yeah, okay, so these papers talk about both natural plant hormones.

Lilly: 1:05

You know the phytohormones.

Jad: 1:06

Right and the synthetic or modified ones the plant growth regulators. So what's the difference and why should we care?

Lilly: 1:12

Well, think of it this way Plant hormones are like the tree's own internal communication system, sending signals all over the place. Growth regulators, on the other hand, those are like the tools we can use to kind of tap into that system.

Jad: 1:25

I see.

Lilly: 1:25

Influence those signals?

Jad: 1:27

Gotcha, so we're understanding the language and also figuring out how to talk back.

Lilly: 1:30

Exactly, and both are essential if you want to understand how trees grow, how they adapt, how they respond to everything around them.

Jad: 1:39

It's like having that secret decoder ring.

Lilly: 1:40

Yeah, it really is. Now. There are tons of different plant hormones and regulators out there, but we'll focus on the main players today, the ones that matter most for you folks in the field.

Jad: 1:50

Okay, perfect Crash course in tree communication. Let's do it. Where do we begin?

Lilly: 1:55

Let's start with what we call the classical five Oxins, gibberellins, cytokinins, ethylene and abscisic acid. These are the foundation, really, Each one with a crucial role in how a tree grows and develops.

Jad: 2:06

All right, sounds good. Let's kick it off with oxens. What's their deal?

Lilly: 2:10

Oxens. Think of them as the construction crew in the tree world. They're all about cell division and elongation, laying down the building blocks for growth and their specialty root development.

Jad: 2:23

So those are the root. Gurus Makes sense, right? Strong roots. That's the foundation for everything Stability, nutrient uptake.

Lilly: 2:29

Exactly Now. Here's a cool thing about auxins. They can be synthesized in a couple of ways In the plants themselves, sure, but also in bacteria.

Jad: 2:38

Wait, bacteria make plant hormones. That's wild. Do they like share the recipe with the trees, or something?

Lilly: 2:44

It's more like they've evolved similar pathways, you know, kind of independently arrived at the same solution.

Jad: 2:50

Oh interesting, Convergent evolution or something.

Lilly: 2:52

Exactly the most active natural auxin is indole-3-acetic acid IAA for short, Got it. But we've also got synthetic auxins that we've created. Some of them are even more potent. Oh wow, so it's like we've hacked the tree's communication system. Yeah, creating these like supercharged signals In a way, yeah, and this is where it gets really practical for arborists. Knowing about these different auxins natural and synthetic, understanding their effects, it can make a huge difference, stimulating root growth in new plantings, for example, or even controlling those unwanted shoots.

Jad: 3:25

OK, so oxen, they're the builders, the root specialists Got it. What about gibberellins? What's their role in this whole tree symphony?

Lilly: 3:34

Gibberellins. Those are the ones that make trees stretch for the sky, responsible for stem elongation, so they play a big part in how tall a tree grows. Plus, they influence things like seed germination and flowering too.

Jad: 3:46

So like the growth spurt hormones basically.

Roger: 3:49

Yeah.

Jad: 3:50

And I remember reading somewhere there are over 130 different types of gibberellins. Why so many?

Lilly: 3:54

It's all about fine-tuning, really. You see, while there are many types, only a handful are what we call bioactive. They have a direct effect on growth, and what's cool is that scientists have figured out how to manipulate gibberellin biosynthesis.

Jad: 4:07

Manipulate how so.

Lilly: 4:09

Oh, they've done some amazing things. One great example is the development of those semi-dwarf varieties of rice and wheat. Oh yeah, I've heard of those. They're shorter, sturdier, less likely to topple over Right, and they produce higher yields. It was a revolution in grain production.

Jad: 4:24

Wow. So just by tweaking one hormone you can totally change how a plant grows.

Lilly: 4:28

It's pretty remarkable, isn't it? And that's why understanding these hormones is so powerful.

Jad: 4:33

Okay, we've got the builders, the oxums and the stretchers, the gibberellins. Now what about cytokinins? What do they bring to the table?

Lilly: 4:41

Cytokinins they're the cell splitting specialists. They team up with auxins, but while auxins are focused on those roots, cytokinins are all about shoot, development, branching, leaf expansion, all of that.

Jad: 4:52

Ah, so they're shaping the above ground structure, but I'm a little confused. I read that they also delay senescence Right. Isn't that like contradictory Promoting?

Lilly: 5:04

growth and preventing aging at the same time. That's a great point, and it really highlights how important cytokinins are for balancing the whole growth cycle. You know, it's not just about growing bigger. It's about staying healthy and vital while you do it. Think of them as like ensuring the tree stays youthful and strong even as it grows.

Jad: 5:19

Got it. So it's all about finding that balance between growth and longevity.

Lilly: 5:23

Exactly and just like with skincare products.

Jad: 5:25

Oh, I like that analogy.

Lilly: 5:26

There are different types of cytokinins, each with their own special properties and effects.

Jad: 5:31

Okay, so we've got the builders, the stretchers and the youthful architects. I guess who's next on our plant hormone all-star list?

Lilly: 5:40

Let's move on to ethylene, the unique one, because it's a gas.

Jad: 5:44

A gas? Wow, that must make it tough to study.

Lilly: 5:47

You're telling me it's much harder to track and analyze compared to the others. But don't let its flighty nature fool you. Ethylene's got a big role to play in some key processes.

Jad: 5:57

I know it's famous for ripening fruit, but the research mentioned it does a whole lot more than that. What else is it up to?

Lilly: 6:04

Well, besides making those bananas turn yellow ethylene is also key in leaf senescence you know when the leaves age and drop and it's involved in stress response and even root development, believe it or not.

Jad: 6:14

Wow, busy little molecule. And speaking of connections, doesn't ethylene also affect how other plant hormones work?

Lilly: 6:21

You're absolutely right. It interacts with auxins, cytokinins and abscisic acid, fine-tuning those growth processes. It's like this intricate dance, with each hormone playing its part in the overall performance.

Jad: 6:31

It's not a solo act, it's a whole collaborative effort. This is getting complex. All right, let's move on to our last classical five hormone abscisic acid. What's its claim?

Lilly: 6:43

to fame, Abscisic acid, often called the stress hormone. It's all about how trees handle tough times drought, salinity, extreme temperatures, you name it.

Jad: 6:51

Wait, I remember reading that abscisic acid is also found in humans and fungi, and bacteria too. What's going on there?

Lilly: 6:57

It's amazing, right. It seems like abscisic acid is crucial for dealing with environmental challenges across many different life forms. In plants, it helps regulate water loss and protect cells from damage.

Jad: 7:08

So it's like the plant's emergency response system.

Lilly: 7:10

Exactly and, just like with emergency responses, there are a couple of main ways that abscisic acid is biosynthesized. Fungi use a direct route from farnesyl pyrophosphate, but plants have a more indirect C40 pathway, starting with a beta-carotene precursor.

Jad: 7:26

So two different paths, same destination. It's fascinating how this tiny molecule is like a universal batten down the hatches signal and for you all out there, the arborists, Understanding how abiotic stress affects tree health and how abscisic acid is involved is crucial.

Lilly: 7:44

Absolutely.

Jad: 7:45

It can help you diagnose problems and figure out how to help trees thrive even in tough conditions.

Lilly: 7:49

Precisely Knowing how this hormone works could be the difference between a tree that flourishes and one that struggles.

Jad: 7:56

All right. So we've covered the classical five auxins, gibberellins, cytokinins, ethylene and abscisic acid. That's a lot to take in.

Lilly: 8:03

It is, and we've just scratched the surface. Yeah, but having this basic grasp of these key hormones, that's a great starting point for understanding how trees grow, how they develop, how they react to their surroundings.

Jad: 8:15

And for arborists, that's powerful knowledge. Right yeah, you can make better decisions about everything. And for arborists, that's powerful knowledge. Right yeah, you can make better decisions about everything Planting, pruning, managing stress, keeping trees healthy overall.

Lilly: 8:24

Exactly.

Jad: 8:25

I feel like I just got a serious upgrade to my tree whispering skills, but I have a feeling there's more to discover in the world of plant hormones. Should we keep going?

Lilly: 8:33

Oh, absolutely. We've only just begun to explore this amazing world. There are many more players to meet, and their roles and interactions are just as crucial as the classical five we've talked about so far.

Jad: 8:44

All right, then let's keep diving.

Lilly: 8:46

Well, one group that's been getting a lot of attention lately is the brassinosteroids.

Jad: 8:51

Brassinosteroids okay.

Lilly: 8:52

Yeah, they're involved in a whole bunch of processes, from cell elongation to stress response. They even seem to have a role in protecting plants from disease.

Jad: 9:02

So like the multi-talented overachievers of the plant hormone world.

Lilly: 9:08

You could say that they're incredibly versatile and there's evidence suggesting they can actually enhance the effects of other hormones.

Jad: 9:13

Oh, really Like what.

Lilly: 9:14

Like oxins and gibberellins, for instance, sort of like a team player that boosts everyone's performance.

Jad: 9:21

I like it. Teamwork makes the dream work, even for trees. What other hidden talents are we uncovering in these newer hormones?

Lilly: 9:29

Well, let's talk about jasmonic acid. That's the plant's security guard. You could say Okay, the protector. Yeah, primarily known for its role in defense against herbivores and pathogens you know, those pesky things that can cause disease.

Jad: 9:42

Right, right. So it's like the tree's personal bodyguard keeping those troublemakers at bay. How does it work?

Lilly: 9:48

Jasmonic acid triggers the production of all sorts of defense compounds. Think of it as the tree's chemical arsenal.

Jad: 9:56

Oh cool, Like what kind of compounds?

Lilly: 9:58

Things like protease inhibitors, which mess with insect digestion, and phytoalexins, which have antimicrobial properties.

Jad: 10:06

Wow. So the tree's not just sitting there passively, it's actively fighting back.

Lilly: 10:09

Oh, absolutely that's impressive.

Jad: 10:11

Are there any other hormones involved in this defense strategy?

Lilly: 10:14

For sure. Salicylic acid is another key player. It's the mastermind behind what we call systemic acquired resistance.

Jad: 10:21

Systemic acquired resistance. That sounds pretty intense. What is that exactly?

Lilly: 10:26

Imagine this A tree gets attacked by a pathogen right in one spot, so salicylic acid steps in and it triggers this chain reaction that basically boosts the tree's immune system. Ah, I see it makes it more resistant to future attacks throughout the entire system.

Jad: 10:42

So it's like the tree learns from experience and becomes better prepared. That's amazing.

Lilly: 10:46

It really is. It's a great example of how plants, even though they don't have brains like ours, can still have these incredibly complex responses to their environment.

Jad: 10:55

OK, I'm officially blown away by plant intelligence. So we've got the defenders jasmonic acid and salicylic acid always on guard. Who else is in this intricate plant hormone network?

Lilly: 11:07

We can't forget about the facilitators Strigalactones. They play more of a behind the scenes role.

Jad: 11:12

Oh right, strigalactones, those are the ones with the potential anti-cancer properties, right?

Lilly: 11:16

That's right. That's one of their more fascinating aspects.

Jad: 11:18

Yeah, I was super intrigued by that.

Lilly: 11:20

But they also have a very important role in regulating plant branching and those interactions with mycorrhizal fungi in the soil.

Jad: 11:28

So stregolactones are like the matchmakers, helping the tree connect with its underground network of fungal friends.

Lilly: 11:34

Exactly they promote the growth of what we call hyphal branches from the fungi which then penetrate the plant roots and establish that crucial connection.

Jad: 11:45

Wow, it's like a whole hidden world of cooperation going on beneath our feet and as arborists we need to understand those interactions.

Lilly: 11:51

Absolutely Knowing how strigolactones influence those relationships, it can help us promote healthy root systems and overall tree vigor. For example, certain soil amendments can actually stimulate mycorrhizal growth.

Jad: 12:04

I see, so we're helping the helpers.

Lilly: 12:05

Exactly, and that in turn helps the tree. It's all connected.

Jad: 12:09

Okay, so we've got the growth promoters, the stress responders, the defenders and now the facilitators. It's like a whole ecosystem of hormones working together to keep a tree healthy and thriving.

Lilly: 12:21

That's a great way to put it. It really underscores the complexity of plant physiology, but I hope it's given you a greater appreciation for the intricate world of plant hormones and growth regulators.

Jad: 12:31

It definitely has, but I have a feeling there might be a few more players in this plant hormone orchestra. Should we keep exploring?

Lilly: 12:38

Of course, we haven't even touched on plant peptide, hormones and nitric oxide yet.

Jad: 12:42

All right, lead the way. I'm ready to meet the rest of the cast.

Lilly: 12:45

Let's delve into the world of plant peptide hormones. They're relatively new on the scene and we're still figuring out all their roles, but we know they're involved in a wide range of processes, everything from regulating cell division to controlling responses to stress and disease.

Jad: 13:01

So, like the up-and-coming rookies, full of potential, ready to shake things up.

Lilly: 13:05

Exactly, and their potential applications are vast. For example, some plant peptide hormones are being explored as biopesticides.

Jad: 13:13

Hold on biopesticides. You mean we could use these natural plant hormones to control pests instead of relying on synthetic chemicals.

Lilly: 13:21

Precisely. It's a much more environmentally friendly approach, and it's just one example of the exciting possibilities that plant peptide hormones offer. Others are being investigated for their potential to enhance plant growth, improve stress tolerance and even boost nutrient uptake.

Jad: 13:37

Wow, it seems like these little peptides have a lot to offer, but you mentioned earlier that they might be species-specific. What does that mean for their practical applications?

Lilly: 13:46

It means that a peptide hormone that works wonders in one plant species might not have the same effect in another, so their development is a bit more challenging. It requires a deeper understanding of the specific interactions between these hormones. Might not have the same effect in another, so their development is a bit more challenging. It requires a deeper understanding of the specific interactions between these hormones and different plant species.

Jad: 14:00

Well, it's like finding the right key for the right lock. Each tree species has its own unique set of peptide hormones that we need to understand to unlock their full potential.

Lilly: 14:10

That's a great analogy and it highlights the importance of ongoing research in this area. The more we learn about these species-specific interactions, the more targeted and effective our applications can be.

Jad: 14:21

Okay, so plant peptide hormones are definitely ones to watch. Who else is on our list of plant hormone superstars? Last but not least, we have nitric oxide. Now, this one's a bit different because it's a gas just like ethylene Nitric oxide. I remember reading that it's involved in a variety of processes, including plant defense and stress responses. But how does a gas molecule even act as a hormone? It seems so different from the others.

Lilly: 14:45

What's fascinating about nitric oxide or NO, is that it can rapidly diffuse across cell membranes, unlike most other hormones that need specific receptors to enter cells. This allows it to act quickly and directly on various cellular processes. Think of it as a rapid response team swiftly moving throughout the plant to address immediate needs.

Jad: 15:04

It's like the plant's emergency broadcast system, sending out an alert signal to all parts of the tree when something's up.

Lilly: 15:11

Exactly and just like an emergency broadcast system, no can trigger a cascade of responses, activating defense mechanisms, adjusting growth patterns or even initiating cell death in specific areas to protect the plant as a whole.

Jad: 15:24

Wow. So this tiny molecule can have a huge impact on the plant's survival. Does it work alone, or does it interact with other hormones too?

Lilly: 15:32

It's a team player for sure. No is known to interact with other plant hormones, modulating their effects and fine-tuning their actions. For example, it can enhance the effects of abscissic acid in drought stress response, helping trees cope with water scarcity even more effectively.

Jad: 15:47

So it's like a master conductor coordinating the actions of the entire plant hormone orchestra to ensure the tree's survival and success.

Lilly: 15:54

Precisely, and for arborists, understanding the role of NO can be incredibly valuable. It gives us insights into how trees respond to stress and could potentially lead to new strategies for mitigating those stresses.

Jad: 16:05

Well, this deep dive has really been an eye-opener. I used to think of trees as these silent, passive beings, but now I see them in a whole new light. They're constantly communicating and responding to their environment in incredibly complex ways.

Lilly: 16:19

It's truly remarkable.

Jad: 16:20

As an arborist, I feel like I have this whole new set of tools to understand and care for trees. It's not just about pruning and fertilizing anymore. It's about working with the tree's own internal communication system to promote its health and resilience.

Lilly: 16:34

Exactly. It's about understanding the language of trees and using that knowledge to help them thrive.

Jad: 16:40

This has been an incredible deep dive. Thanks so much for sharing your expertise with us.

Lilly: 16:44

It's been my pleasure, always happy, to talk about the wonders of plant science.

Jad: 16:48

And to our listeners, thanks for joining us on this journey into the world of plant hormones. We hope you've gained a newfound appreciation for the complexity and intelligence of trees. Until next time, keep exploring.

Roger: 17:04

That's it for today's episode. We hope you enjoyed learning about the role of phytohormones in plant growth and tree development. If you found this interesting, don't forget to share the episode with fellow tree enthusiasts. Join us next time for more deep dives into the fascinating world of plants, trees and everything in between. Until then, take care and keep exploring the science that helps our green world thrive. Thank you.