AYESHA RASCOE, HOST:
Be quiet and listen. Your plants might be trying to tell you something.
(SOUNDBITE OF POPPING NOISES)
RASCOE: That's the sound of a thirsty tomato plant captured by scientists at Tel Aviv University. They were able to record all kinds of plants that make sounds when stressed. Biologist Lilach Hadany led the study and joins us now from Tel Aviv. Welcome.
LILACH HADANY: Thank you.
RASCOE: I am a known plant killer, and so I forget to water them, but I have not heard them making sounds or screaming. So is my hearing bad, or is there a reason why I'm not hearing them screaming out in thirst?
HADANY: So, of course, if they were doing these actual sounds that we are hearing now, we would have known that a long time ago. The sounds that the plants are emitting are too high for humans to hear. Humans usually hear up to around 16 kilohertz. Plant sounds start from around 40 kilohertz up to around 80.
RASCOE: So then the sounds that we were just hearing - those are sounds that have been boosted for the human ear?
HADANY: These sounds are only made for demonstration. So we recorded the plant sounds using very sensitive ultrasonic microphones. And then we use the computer to convert them to human hearing range.
RASCOE: Do we know how the plants are actually making the noise?
HADANY: So we are not completely sure about that, but we think that it involves air bubbles appearing in the water transport of the plant, emitting a very brief ultrasonic click.
RASCOE: Have you found that there are a range of sounds coming from different plants?
HADANY: Plants emit different sounds under different circumstances, so the sounds are informative. We can tell by the sound if it's a tomato or a tobacco plant and if the tomato is dry, and if it is dry, is it slightly dry or very dry? So we can understand that using only the sounds.
RASCOE: Who is the intended recipient of these noises?
HADANY: So that's the most exciting question. We know that there are animals that are capable of hearing these sounds, like moths and bats and mice. So if a moth is coming to lay eggs on the tomato, it can lay its eggs on a plant that would serve as a good host. Another direction is that other plants may be responding to the sounds. The stress of one plant is most important to the other plants neighboring it. If they know that a nearby plant is drying up, then this is time to prepare. And finally, it might also be useful for agriculture. If farmers can monitor the stress of the plants without touching them, we can use water more efficiently or potentially herbicides.
RASCOE: And so is that the goal of your research, that it would be possibly applied to agriculture? Are there any other applications for the research?
HADANY: So I think the goal of my research is to understand the world better. I think these results suggested there is an additional layer of information, of acoustic information, between plants and their environment. The sounds are out there, and we need to interpret them.
RASCOE: So if we have plants at home, is there a way we could just turn up a recorder and try to see if they're getting the water properly, or this is only in the lab?
HADANY: There are cheaper and simpler methods.
RASCOE: To find out if the plant is drying out.
HADANY: At home, you don't need these sensitive microphones that we are using. But even simpler sensors that can detect ultrasonic clicks can be useful.
RASCOE: That's Lilach Hadany, a biologist at Tel Aviv University. Thank you so much for joining us.
HADANY: Thank you. Transcript provided by NPR, Copyright NPR.
