322: Screaming Plants

[00:00:03] Speaker A: Welcome to brain junk. I'm Amy Barton. [00:00:05] Speaker B: And I'm Trace Kerr. And hold onto your hats, everybody. Today we're gonna talk about screaming plants. [00:00:12] Speaker A: Oh, that sounds delightful. [00:00:18] Speaker B: It's like a horror movie. And Amy's like, oh, that sounds like fun. Let's talk about it. [00:00:23] Speaker A: I don't think they grow here, whatever they are. That sounds tropical. So I'm down. Let's talk about it. [00:00:29] Speaker B: Oh, Oakwell, aren't you? I could be wrong. Yeah. So. Okay, for real, though, it's less a scream and more of a snapping or a pop sound, but still, I know I am falling into the. What is it? Click bait. I just click baited. Take that. Yeah. So Beckett sent me a tumblr post about plants screaming. And so this person is saying, did you know that plants can scream? And they do it at this sort of frequency? And then somebody else said, but wait, dogs and cats hear at that frequency. Can they hear plants screaming? [00:01:04] Speaker A: I hope so. And I hope not. Maybe. [00:01:06] Speaker B: Well, yeah. And so Beckett sent it to me and said, is this true? At, like, 02:00 in the morning? [00:01:11] Speaker A: We all want you to find stuff out for us. [00:01:16] Speaker B: Because, you know, it's like, I can't. It's like an itch. I gotta scratch it. Okay, so this goes straight to biologists at Tel Aviv University. And plant torture. That's what we're going to be talking about today. Okay, the paper. Sounds emitted by plants under stress are airborne and informative. Yes. They make people broken. No, they're airborne and informative. That came out in the journal cell in March of 2023. And so we know plants make all sorts of changes to themselves in response to stress and environmental harm. You had one about grass, isn't it? Yeah. And smells to attract bugs to defend the plant. [00:01:56] Speaker A: Yeah, they're interesting. [00:01:58] Speaker B: Right. And they can change the amount of sugar they produce in their nectar. I did that one on flowers. When they heard the buzzing of bees, they would make sweeter nectar. [00:02:08] Speaker A: That's right. [00:02:10] Speaker B: And then the bees would come and drink from those flowers. Well, this is kind of going in. [00:02:15] Speaker A: That same direction, except down the help save us direction. [00:02:19] Speaker B: Well, yeah, kind of. So scientists led by Professor Leelak Hadane wondered if plants could also make a sound. So, you know, it's like, okay, we know they can make smells, and we know they can make sugar. Can they scream when in danger? [00:02:35] Speaker A: I would not have thought to ask that question. [00:02:38] Speaker B: I know. Me neither. And even if the sounds are made by accident or as a response to, say, drying out during drought, when plants dry out there are air bubbles that expand and pop under the skin of the plant. That's the sound that it's make. So those are sounds to act as a cue to the environment that might benefit the plant. So even if they're by accident, maybe it's accidentally screaming. They thought, well, okay, let's look into this. So the study used tobacco and tomato plants, and they seem to be the ones that tend to get the most abuse in plant studies, I've noticed. [00:03:14] Speaker A: Yes. I do feel like tomatoes were one that had a defense mechanism. So that was a good group to start with. [00:03:20] Speaker B: Yeah. And they grow fast. [00:03:22] Speaker A: They often have a bug population. [00:03:25] Speaker B: They do. So, yeah. So they took the tomato plants and the tobacco plants, and they put them in an acoustic chamber and in a greenhouse to record what turned out to be ultrasonic sounds. Oh, yeah. So let me give you a quick review of ultrasonic sound. So something like a dog whistle. That is a frequency that is high, and it's so high that, like, we can't hear it, but dogs can hear it. [00:03:50] Speaker A: Gotcha. [00:03:50] Speaker B: Okay. And the researchers used AI to analyze the sounds made by plants. Okay, so there's a picture, and you've got a plant. It's in a pot. They have two microphones, so you get, you know, sound from multiple directions so they can triangulate that sort of thing. And they're recording sounds, and then they feed those sounds into a computer. And the computer is kind of processing what these sounds are because we can't hear them. And then they figured out that this AI could use the information that they recorded to accurately predict what was stressing the plant out. [00:04:31] Speaker A: It's like phineas and Ferb where they make the translator so that they can find out what their pets are saying. [00:04:38] Speaker B: Yes. [00:04:38] Speaker A: I feel like Ferb is running this experiment. What are the study authors? [00:04:45] Speaker B: Yeah, well, no, let me go back up. No, nope. Not phineas, not ferb. Yeah, so let's get to the plant. Torture. So they did two different things. They drought stressed them, so, you know, they were watering them less, and then they also cut branches. [00:05:00] Speaker A: Torture. [00:05:01] Speaker B: Yeah. And they had a lucky group of control plants, so they did not get tortured, but they did get recorded. They also recorded an empty pot with dirt in it. [00:05:11] Speaker A: I have so many questions, and I wonder if they're going to be like the seagulls, where some of the seagulls were exposed to aversive, scary predation sounds. So then the other seagulls that lived in the clutch next to them that didn't hear the scary sounds but lived with the scared siblings, they all came out different. [00:05:31] Speaker B: Yeah. So this is. I'm gonna make a long story really short. Plants do make detectable sounds when stressed. [00:05:38] Speaker A: Wow. [00:05:39] Speaker B: You can hear it for up to nine to 16ft away and almost 50 sounds per hour. [00:05:45] Speaker A: Oh, wow. [00:05:45] Speaker B: But it's not screaming. It's more of, like, pop sounds. And between 20 to 100 khz, but mostly in the 49.6 to 54.8 khz range range. So just for reference, a human hears from about 20. About 20 khz. [00:06:07] Speaker A: Okay. [00:06:08] Speaker B: Kilohertz is getting up high, really high. Okay. Babies hear a little bit farther past that 20 khz, but very quickly, they lose that. And then as we age, we lose hairs in our ears that help us detect stuff. So, for example, I have a dryer that's older than Goddesse, and I load it in the towels, and I went about my business, and Cam says, what is that screeching? And I'm standing there, and I was like, I don't hear any screeching. And then I remembered Anson had been over, and he said, your dryer is killing me. So I went downstairs, I closed the laundry room door, and Cam says, oh, thank God. That was awful. I can't hear it. [00:06:53] Speaker A: My parents had an air purifier like that. The family was all over and were like, is there a turbine in that thing? What is going on? And they're like, what? They truly innocently had no idea what we were talking about. And so it did make me feel young for a moment. [00:07:09] Speaker B: Yeah. And if I get right on top of it, I can kinda hear it. So at the wonderfully ripeled age of 50, I'm probably not hearing anything over about 16 khz versus that 20 khz that, you know, is possible for an adult. So. [00:07:28] Speaker A: So if plants are trying to warn you of danger, it's not gonna help. [00:07:31] Speaker B: No, I won't. I won't. I won't hear it. Maybe a baby might hear what's happening, but here's the thing. They're not really warning anybody. It's more of a reaction to something that they're experiencing. So. Okay, the question Beckett had was, can animals hear the shouting of plants? Well, a dog can hear up to about 60, bat up to 120, cats up to about 85. And like I said, plants are making this sound between 21 hundred, but more in that 50 to 55 range. [00:08:06] Speaker A: Okay, so maybe. [00:08:07] Speaker B: Yeah. So odds are it's kind of noisy out there when, say, there's a windstorm and plants have broken branches, or even with climate change, if it's really dry and it hasn't rained. Some plants, at least, tomato, tobacco, wheat, corn, grapevines, and the pincushioned cactus are making noise. Those are the ones that they've studied. Yeah. So where is the sound even coming from? [00:08:29] Speaker A: Yes. Do tell. [00:08:30] Speaker B: Because it's not a tiny mouth. It's not going, and it's not snapping its little fingers. The frequencies of sound seem to correspond to the trachea diameter. Now, the trachea I'm talking about is not like your throat. So inside a plant, fluid moves around inside, in the xylem, through special cells called vessels. Okay. And the vessels take water and sugar. Maybe you're having a flashback to, like. [00:08:55] Speaker A: Fourth grade as you're drawing this. [00:08:58] Speaker B: They take water and sugar around the inside of the plant. Okay. In these special cells. And there's air inside those cells, a little bit included along with the liquid. Right. When you cut a stem, the air in those cells escapes, making that kind of popping sound. Yes. [00:09:22] Speaker A: Okay. [00:09:22] Speaker B: And when a plant is drying out, the cells shrink and there's less liquid, so there's more air. And then gradually, it's also making that popping sound as the air escapes. [00:09:40] Speaker A: Oh. So what it was, I was wondering is if it's like, when you kink a hose that has some water in it and you unkink it and it makes that little crack sound, and it's analogous, is similar. [00:09:50] Speaker B: Yeah. It's a little. It's a little burst. Yeah. Yep. It is. At least even in the study, like, in this paper that's been published, they said there are limitations to our current understanding of just how exactly sound is being made, and it needs more investigation. [00:10:06] Speaker A: So it could be more purposeful. It might not be an accident. [00:10:10] Speaker B: Yeah. I mean, they don't think that one is, like, a drought starved plant is making these popping because, I mean, what are you gonna tell the plants around you? We're all dying. I mean. [00:10:21] Speaker A: Yeah. Flee for your lives. [00:10:24] Speaker B: Exactly. So they're thinking a good application might be if you had sensors in, say, a field, you could monitor the plants. And if you're getting a lot of these popping noises, that maybe that means you need to. Water. [00:10:38] Speaker A: Mm hmm. [00:10:39] Speaker B: Yeah. [00:10:39] Speaker A: You could record and play the sounds for your pet and teach your pet that they should alert when they hear that popping, and then just go have them sit in the field once a day now. [00:10:48] Speaker B: So I went back to Beckett, and I said, yes, it's probably true that dogs and cats can hear. I mean, like, on the whole, if you're out in the yard and there's no wind and there aren't broken branches and everybody's hydrated. You're probably not hearing any popping. But then Beckett said. So is this why cats are knocking vases of plants or pots of plants off of things? Because they're little psycho killers and they like to hear the plants go pop, pop, pop. [00:11:17] Speaker A: I absolutely would believe that they're providing themselves with some cheap entertainment. [00:11:21] Speaker B: Yeah. They're like, I heard it screaming. [00:11:28] Speaker A: That's excellent. Yeah. Cats are murderous little creatures. [00:11:35] Speaker B: Yeah. So who knew? Tumblr. [00:11:38] Speaker A: That's unexpected. Yeah. I think that's delightful. And now there's a little symphony for all the animals that can hear it. A symphony of cracks. [00:11:49] Speaker B: Yes, but only on the green part of plants. They did find that your trunk, like on a grapevine. The old part, part of the woody part. Those aren't making any noises, which that. [00:12:02] Speaker A: Makes sense if it's the fluid and air parts of things that's making is the function. [00:12:08] Speaker B: Yeah. [00:12:09] Speaker A: Excellent. [00:12:09] Speaker B: Who knew? [00:12:10] Speaker A: Not me. [00:12:11] Speaker B: Just like if you stab a human being, they make weird, squirty noises. We're not doing it for any particular reason. [00:12:18] Speaker A: We just wanted to know what it sounded like. [00:12:20] Speaker B: Yeah. [00:12:25] Speaker A: All right. Well, we are on Facebook and Instagram as brain junk podcast. 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