MADDIE SOFIA, HOST:
Hey, everybody. Maddie Sofia here with Emily Kwong.
EMILY KWONG, BYLINE: Hey.
SOFIA: So today, we have a Micro Wave inspired by a pair of SHORT WAVE listeners and your real-life friends, Emily.
KWONG: I do have real friends. Yes.
SOFIA: Yes, you do (laughter). Amy Wurzburg (ph) and Amanda Drewry (ph).
KWONG: Yes. Amy and Amanda, like a lot of us, are trying to grow plants.
AMY WURZBURG: We have five plants, all are herbs.
KWONG: And every morning as Amy waters the plants, she talks to them. She'll say...
WURZBURG: Good job, sage. Thyme, I'm really seeing some good growth here.
WURZBURG: And parsley's looking a little wilty but, parsley, I believe in you.
SOFIA: I wish somebody believed in me as much as Amy believes in parsely. You know what I'm saying, Kwong?
SOFIA: So why does Amy talk to her plants?
KWONG: Well, she believes that on a chemical level, it helps them grow big and strong. And - yeah - and Amanda does not agree.
AMANDA DREWRY: I don't think that talking to plants really makes that much of a difference.
WURZBURG: So what about the fact that our cilantro is dead because you were mean to it?
DREWRY: Well, I don't like cilantro, so, you know, I'm fine with it.
WURZBURG: I'm just saying. All the rest of our plants are doing OK except our cilantro.
DREWRY: But I also don't like parsley, and parsley is fine.
SOFIA: (Laughter) Honestly, I'm on Team Parsley right now, Kwong.
KWONG: As you should be. And Amy and Amanda texted me and were like, Emily, please resolve our couples' squabble. Is there scientific evidence around the benefit of talking to plants?
SOFIA: So is that what our Micro Wave is about today, plant communication?
KWONG: You better believe it. Plants bioacoustics and whether talking to plants actually makes a difference.
(SOUNDBITE OF MUSIC)
SOFIA: All right, Emily Kwong, you are here for another Micro Wave.
KWONG: Beep, beep, beep.
SOFIA: Short little episodes where we read some listener mail at the end. And we're talking about what science has to say and not say about plant bioacoustics. And this question that I can't believe I'm asking, which is, does talking to plants impact their growth?
HEIDI APPEL: It is probably the most common question I get from the public.
KWONG: This is Heidi Appel, professor of environmental sciences at the University of Toledo. And just to get this out of the way, there is no conclusive scientific proof that talking to your plants helps them grow.
SOFIA: All right. There we go. Episode done. Boo boo boo-doom (ph), we out of here.
KWONG: Well, hold the phone, Sofia. It's not that simple because Heidi is one of the few people who has studied plant response to sound.
APPEL: They have a sense of vision, sight, smell and taste.
KWONG: And scientists, including Heidi, have found evidence that plants can detect sound too.
APPEL: All life has some form of mechanoreception.
KWONG: Meaning, they can sense stimuli from their environment like touch, pressure and vibration. We humans have pressure receptors on our skin, and it turns out that plants can sense pressure too.
SOFIA: This is very cool. I'm getting into this now.
KWONG: Yeah. Through these special proteins called mechanoreceptors that can send a signal that sets off a chain of events telling the plant how to respond.
SOFIA: So like if a bug lands on them or something?
KWONG: Yes. And the plant will perhaps release a chemical to defend itself.
SOFIA: Oh, plant panic.
KWONG: That's right (laughter). So these mechanoreceptors are really important for telling the plant what's up in its environment. And plant scientists think these mechanoreceptors may play a role in helping plants pick up vibrations, including the vibrations caused by sound, you know, sound waves.
APPEL: We've known for a long time that plants can respond to single tones or even music, and they can respond by growing a little differently or their seeds may germinate at a different rate. But we never understood why they would do this. Why would they have this capability? And that's where my work with collaborator Rex Cocroft at the University of Missouri comes in.
KWONG: So a few years ago, Heidi and Rex put together a little study asking if a plant will respond to vibrations in their environment. And the vibration they chose to test was caused by a caterpillar chewing.
(SOUNDBITE OF CATERPILLAR CHEWING)
SOFIA: What an adorable experiment.
KWONG: Munching up the leaves of a plant, specifically a mouse-ear cress, which Heidi had growing in the lab. And these vibrations are super subtle. The leaf is sometimes moving like one ten-thousandth of an inch as the caterpillar bites down. Rex and Heidi then played the vibration.
SOFIA: The vibration of the lonomia caterpillar?
KWONG: Right. Back to other cress plants who had not been munched on at all and then expose those same plants to real caterpillars and measure their chemical response. And the plants that had heard the recording beforehand produced more insect defense chemicals.
SOFIA: Oh, so, like, playing the sound before the real caterpillar kind of like primed the plants.
KWONG: Yeah. This experiment showed that plants pre-exposed to the sound of a chewing caterpillar produced a different response.
SOFIA: More plant panic, if you will.
KWONG: (Laughter) Yes, I will. Which suggested, you know, that plants, these plants are sensitive to the sounds of this predator, the caterpillar. And then they tested other vibrations on the plant - wind, other insect-eating noises that were not as threatening. And wouldn't you know? The plants did not respond.
SOFIA: Like, chemically, they didn't respond?
SOFIA: So, OK, so does that mean they have, for lack of a better term, selective hearing?
KWONG: More like selective responding.
KWONG: Plants do respond to sound but only to sounds they've evolved to respond to, if that makes sense.
SOFIA: OK. Yeah, totally.
KWONG: In this case, a caterpillar chewing.
SOFIA: Got you. OK. So Caterpillar chewing, yes. But what about a human voice?
KWONG: Well, that hasn't been comprehensively tested.
KWONG: And Heidi thinks it's not likely.
APPEL: A plant will be experiencing noise in the sense of wind or a calling bird or a singing entomologist (laughter). But they will be tuned to only the things that are important to them.
KWONG: Right? And we don't know if one of those things is a human voice. We also don't know the threshold of what they detect, and we don't know if they'd have a reason to respond.
APPEL: So should you talk to your plants? Sure, why not? Is it going to help them grow better, your voice alone? No, I don't think it's going to. However, if you connect emotionally with your plant better because you're talking with them, that means you're probably going to take better care of it. And therefore, talking to your plants indirectly could be helpful.
SOFIA: That's kind of beautiful. I do honestly feel emotionally connected to my plants, Kwong. I'll say it.
KWONG: Did you name them?
SOFIA: No because they're like clones. So I don't want them to get any ideas like Clone 1, Clone 2, you know what I mean? I try to keep a distance, you know? I don't want to have favorites.
KWONG: Well, Maddie, it's great to hear you're experimenting at home because Heidi says there's a lot we could stand to learn about plants.
APPEL: Plants have about 80% of the biomass on earth, and we are doing a terrible job taking care of it. And the ecosystem services they provide are so important to our long-term survival. So if people can think of plants with more affection and appreciation for what they do, I think we will be much better off as humans.
SOFIA: Wow, Kwong, that's kind of beautiful.
KWONG: So, Amy, you were kind of right.
SOFIA: Yeah, kind of.
KWONG: Not that I'm taking sides, obviously.
SOFIA: Right. You clearly are.
KWONG: Both my friends.
SOFIA: You know - both my friends. You know who else leaves us off as better humans, Emily? Our dear SHORT WAVE listeners.
KWONG: Yes. It is listener mail time, where we read notes from the inbox sent by you. This one is from Stephanie Peivers (ph) in Rancho Cucamonga, Calif. Stephanie writes, I offer extra credit to my sixth-grade science class to listen to one of your episodes about once every week or two.
SOFIA: Love it.
KWONG: If I forget to offer it, many students start clawing at me...
KWONG: ...With tiny little sixth-grade claws.
SOFIA: Yeah, definitely.
KWONG: Based on - I assume. Based on your mosquito episode last week, I received this feedback. If I ever meet this Maddie person in real life or in the comments on SHORT WAVE or on an email, then tell her to 1v1 me in Minecraft Battle Royale.
SOFIA: Oh, my God, another Minecraft challenge from a listener. I think I need to get into this, Kwong.
KWONG: The people are calling.
SOFIA: (Laughter) That's true.
KWONG: Thanks for making distance learning teaching easier. That's Stephanie in California.
SOFIA: Love it. So good. So good. All right. Next up, we got a ton of listener notes after our episode about the science behind ripening fruit in a paper bag featuring our one and only producer, Brit Hanson.
KWONG: Ow, ow.
SOFIA: Like this one from Kiara Marguerita (ph). And it says, it seems like you forgot to mention the most famous ripening combo, at least where I am from, kiwis and apples. You know, the truth is, Brit loves Kiwis, too.
SOFIA: You know that, right?
KWONG: Brit's a fruit universalist.
SOFIA: That's true. That's true. She continues, my father is a kiwi producer in Italy. We would put boxes of unripe kiwis on top of boxes of apples and let the magic happen.
KWONG: It's like the peanut butter and jelly of fruit.
(SOUNDBITE OF MUSIC)
SOFIA: (Laughter) All right. That is it from us, our latest Micro Wave. Thank you to our listeners. And thank you to you, Emily Kwong.
KWONG: Always, Maddie Sofia.
SOFIA: Today's episode was produced by Brent Baughman, edited by Viet Le and fact-checked by Ariela Zebede. Thanks for listening to SHORT WAVE from NPR. [CLARIFICATION: An earlier version of this episode stated that Heidi Appel considers plants "sentient beings." Appel's view is that while plants have the capacity for sensations, they are not necessarily capable of self-awareness.]
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