Roger: 0:02

Talking Trees with Lily and Jad. Welcome to Talking Trees. It's Monday and today we'll be diving into a fascinating topic in tree biology reaction wood. This special type of wood forms when trees attempt to realign themselves after tilting or leaning. In this episode, we'll explore the morphology, anatomy, ultra structure of reaction wood at different levels, from macroscopic to microscopic. We'll also look at the differences between reaction wood and regular wood in both angiosperms and gymnosperms, and how different tree species respond to stress by producing various types of reaction wood. Let's dig into the science behind how trees adapt to their environment.

Jad: 0:51

Welcome back to the Deep Dive, where we really get into the nitty gritty of well. Today it's trees.

Lilly: 0:57

That's right. Reaction wood specifically, we're going deep into how it actually forms.

Jad: 1:01

We've got all this research and, honestly, some of it surprised even me. So, arborists, get ready, because I think you might learn something new today.

Lilly: 1:08

It's one thing to see reaction wood out in the field, right but when you understand the cellular level, how it all works, changes how you see things.

Jad: 1:16

And having microscopic vision or something. Okay, so basic question. First, trees obviously can't just like stand up if they fall over. How important is this reaction wood thing for them to, you know, actually survive.

Lilly: 1:28

Oh, it's essential. Think about it. A tree needs sunlight right. If it's leaning, can't reach the light. Reaction wood is how it adjusts, stays strong, all that.

Jad: 1:37

They're built in way to stay upright, and so we've got hardwoods, we've got softwoods. They don't approach this the same way, do they?

Lilly: 1:44

Different strategies. Hardwoods they develop tension wood. Softwoods they go for compression wood. Same goal, different methods.

Jad: 1:51

Okay, I'm intrigued. Hit me with some tension wood facts. What's the like star of the show there?

Lilly: 1:57

It's all about the G layer, that's gelatinous layer. Basically it's almost all cellulose. But how that cellulose is arranged, that's what does it.

Jad: 2:05

Hold on Cellulose. That's just plant cell walls. What's so special about it in this G layer?

Lilly: 2:11

You're right, it's common. But in the G layer it forms these bigger crystals, denser, and they line up with the wood fiber maximum pulling power.

Jad: 2:20

Tiny little cables all pulling tight to straighten the tree out.

Lilly: 2:24

That's a great way to put it, and it gets even wilder Used to be. We thought it was pure cellulose, this layer. Nope, there's other stuff in there Xyloglucan, even some Ramno, Galactura and I.

Jad: 2:33

Now, those are some words I haven't heard in a while. What are they doing in there?

Lilly: 2:36

Honestly still figuring that out.

Jad: 2:45

Xyloglucan, that's like the glue between plant cells, and then that ramno. Well, it's a pectin, usually in softer plant parts, so more complicated than we thought, more than just cellulose.

Lilly: 2:49

It's got this whole team making it work exactly now.

Jad: 2:50

Compression wood completely different story all right, let's hear it no g layer. So what's their trick?

Lilly: 2:56

they go for well just being tough compression wood cells.

Jad: 3:00

Their walls are way thicker and they pack in more lignin lignin that makes wood well woody, pack in more lignin, Lignin that makes wood Well, woody right. So more lignin, stronger push.

Lilly: 3:08

Basically, but it's not that simple either. The lignin itself. It's structured differently in compression wood like not just more bricks but better mortar too.

Jad: 3:16

So we've got hardwoods pulling, softwoods pushing, all happening at the microscopic level. But how does it actually work that G-layer, the tension wood one? How is it making that pulling force Million?

Lilly: 3:28

dollar question, and you know it's been debated for ages even now. No easy answer. Two main theories, though both got some evidence backing them up.

Jad: 3:36

Lay it on me. What are we talking about?

Lilly: 3:38

So first one swelling hypothesis Basically, the G-layer as it matures, it sucks up, water swells up right, pushes against the rest of the cell wall. That forces the other parts to shrink lengthwise and that's the pull.

Jad: 3:50

So it's using pressure like a I don't know a hydraulic thing, almost.

Lilly: 3:55

Kind of, and there's been studies where they like isolate those fibers, get rid of the G layer with enzymes. The other parts they shrink up.

Jad: 4:02

Point for team swelling. Ok, what's the other side of the argument?

Lilly: 4:05

Shrinking hypothesis. This one's different. It says the G layer itself shrinks as it gets older, like a muscle contracting. See, that's the pull.

Jad: 4:14

Not pushing from the inside, but pulling directly.

Lilly: 4:16

Yep, think, like those plastic wrap things, you pull them tight, they shrink lengthwise. That's kind of the idea here.

Jad: 4:24

Two totally different ways to get to the same result, so which one is right?

Lilly: 4:27

That's the thing, Maybe it's not either. Could be both happening. Like G-layer shrinks first gets that initial pull, then maybe it swells, adds even more oomph.

Jad: 4:36

Double whammy of tree straightening power Makes sense. Trees aren't exactly known for wasting effort.

Lilly: 4:41

Exactly, and this is important. It's not just the G layer changing Cellulose microfibrils, they're different too in both tension wood and compression wood.

Jad: 4:50

Okay, now we're getting seriously tiny Microfibrils, remind me.

Lilly: 4:54

So those are like bundles of cellulose molecules, yeah, imagine like cables giving wood its strength, building blocks basically. What's interesting is their size, how they're arranged. It's all different in reaction wood, meaning there's even more going on than just how much cellulose or lignin there is.

Jad: 5:12

So it's not just what you've got, but how it's put together the whole. Like architecture of the cell wall matters.

Lilly: 5:17

Exactly. It's crazy complex how wood forms cellulose lignin, all these little parts working together in ways we're just starting to grasp, you know.

Jad: 5:25

It's kind of mind-blowing all this like microscopic stuff, but it affects the whole tree.

Lilly: 5:30

Right, and yeah, scientists are still working out the fine details of how it works, but what it does, that's huge, especially for folks working with trees directly, like arborists. Right?

Jad: 5:41

Rubber meets the road. So if I'm out there preening, what difference does knowing all this make?

Lilly: 5:45

It's about understanding how the tree will react to what you do, whereas the tension would likely to be. That kind of thing Helps you make better pruning choices, avoid bark inclusion, all that Especially with trees that have a history of leaning, you know.

Jad: 6:00

It's more than just lop off a branch. Got to think about the stress it's been under, how the tree will grow after. What about if a tree's been leaning for a while? Does all that reaction? Does that change the wood itself over time?

Lilly: 6:13

Big time. Something to watch out for, tension wood especially. It can be denser, stronger in tension than regular wood, yeah, but also more prone to warping, splitting that kind of thing.

Jad: 6:24

So that leaning tree, it's not just how it looks. The wood itself might be different.

Lilly: 6:28

You got it. Got to factor that in Cabling bracing, even if you're taking the tree down, knowing where that reaction wood's likely to be based on how it's grown. That's key.

Jad: 6:37

Like you're reading the tree's history, how it's dealt with. Stress, all of that.

Lilly: 6:41

Exactly, and it's not just about like avoiding problems either. Think about shaping trees. Arborists have been using this stuff for centuries, even before they knew the science you know right, pruning a certain way, staking, you can make a tree grow how you want. And now we're getting even better at it. Understanding the how and the why of reaction wood makes those techniques even more precise, helping trees grow stronger, more resilient.

Jad: 7:05

Really working with the tree.

Lilly: 7:06

That's it. It's all about remembering trees. They're alive. They respond this reaction. Wood. It's a perfect example of that. The more we dig into the details, the more you appreciate how amazing they are.

Jad: 7:18

It's kind of humbling when you think about it.

Lilly: 7:20

It really is, and it's why we got to keep learning. You know, the more we know about how trees work, down to those tiny details, the better we can take care of them, whether it's a young one just starting out or you know some big old thing in the middle of the city.

Jad: 7:34

Well said. So reaction wood, it's not just some weird side effect, it's like a whole story about how trees thrive.

Lilly: 7:41

Absolutely. It's evolution in action, right there in the wood itself.

Jad: 7:44

Well, thanks for that deep dive. I know I learned a ton.

Lilly: 7:47

Anytime Trees, always something new to discover with them, that's for sure.

Jad: 7:51

And for everyone listening. Thanks for joining us.

Roger: 8:04

We'll see you on the next deep dive. Thanks for joining us on talking trees. We hope today's exploration of reaction wood gave you a deeper understanding of how trees adapt and respond to their environment. A big thank you to all our supporters. Your continued support allows us to keep bringing you these detailed discussions and expert insights. Until next time, keep learning and appreciating the wonders of trees and thank you again for being a part of the Talking Trees community. You.