Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey
Speaker 1: brain Stuff, I'm Lauren Vogelbaum, and this is another classic
Speaker 1: episode from our former host, Christian Sager. This one deals
Speaker 1: with a question to which the answer may seem obvious,
Speaker 1: but research has made more complicated. Our plants conscious. Hey,
Speaker 1: brain Stuff, it's Christian Sager. So there's this old episode
Speaker 1: of Star Trek called Wink of an Eye. You may
Speaker 1: have seen it. There's this race of aliens that live
Speaker 1: in hyper sped up acceleration. So when the crew of
Speaker 1: the Enterprise appears to meet up with them, they seem
Speaker 1: so slow that they're unable to move. Now, imagine that
Speaker 1: scenario if you were the aliens, wouldn't you assume humans
Speaker 1: were inert objects with no consciousness. Now let's take this
Speaker 1: and apply it to our relationship with plants. When we
Speaker 1: watch videos of plant life sped up, we see their
Speaker 1: lively movement. But even though plants move and respond to stimuli,
Speaker 1: they're not conscious. Right, Otherwise, every time we ate vegetables,
Speaker 1: we'd be causing them pain. Wait, wait a minute, can
Speaker 1: plants feel pain? Well? Okay, there was this guy once.
Speaker 1: His name was Charles Darwin. You might have heard of him,
Speaker 1: and he once proposed something called the root brain hypothesis.
Speaker 1: He proposed that the tip of a plant's root could
Speaker 1: act like a brain does in some animals, receiving sensory
Speaker 1: input and directing movement. In the years since Darwin made
Speaker 1: this proposal, there's been a growing movement in science called
Speaker 1: plant neurobiology, and it debates the way we think about
Speaker 1: plants and consciousness. Other scientists hate this term, but who cares,
Speaker 1: because here's some of the things we know about plants
Speaker 1: because of this really unusual research. Let's start with plant senses.
Speaker 1: We know that plants have a variety of sense, some
Speaker 1: that can actually act as analogs to our site smell, touch, taste,
Speaker 1: and hearing. In fact, there's evidence that when plants hear
Speaker 1: the sound of a caterpillar chewing on a leaf, they
Speaker 1: respond defensively by producing chemicals like mustard oil. This happens
Speaker 1: even if the sound is a recording and nothing is
Speaker 1: eating the plant. Creepy, right, Plants can also communicate sometimes.
Speaker 1: Plant chemical production is like a method of communicating with
Speaker 1: other plants. So here's an example. That smell of freshly
Speaker 1: cut grass that we all know that's actually a distress
Speaker 1: call to warn other plants of danger. It's true in gardens,
Speaker 1: no one can hear you scream. Now, when this distress
Speaker 1: call reaches other plants, they will also emit the chemicals
Speaker 1: to warn their neighbors as well, and these calls can
Speaker 1: even work on different species of plant. For instance, a
Speaker 1: sage plant can signal a tobacco plant to emit an
Speaker 1: odor that's not just to animals that are eating the sage.
Speaker 1: All right, So you hear the term plant neurobiology, and
Speaker 1: you say, but plants don't have brains. Well, one of
Speaker 1: the reasons why many scientists hate that term is because
Speaker 1: plants don't have neurons, but they do produce neuroactive chemicals
Speaker 1: that act like those in the human brain. Glutamate receptors
Speaker 1: form memories and humans, and they're also found in plants,
Speaker 1: and some hormones are transported around plants similar to how
Speaker 1: neurotransmitters move through animal brains. Likewise, some plants are vulnerable
Speaker 1: to drugs that disrupt neurotransmitters in the human brain, like
Speaker 1: prozac or meth amphetamines. They eat even produce their own ethylene,
Speaker 1: which is possibly used as an anesthetic when they're stressed out.
Speaker 1: Plants even have a kind of nervous system, and that
Speaker 1: may allow information to travel around the plant via electrical signals.
Speaker 1: So if plants have sort of brains, do they remember stuff? Well? Yeah,
Speaker 1: plants also have their own kind of memory. In fact,
Speaker 1: there's a plant called the Mimosa pudica plant, and it
Speaker 1: closes its leaflets immediately after they're touched. But because this
Speaker 1: requires energy, the plant won't do it if it's unnecessary. However,
Speaker 1: when researchers dropped potted mimosas fifteen centimeters onto foam, the
Speaker 1: plants learned that the fall wasn't dangerous, so they stopped
Speaker 1: closing their leaves. Even crazier, after one month, the plants
Speaker 1: still remember that the drop wasn't dangerous and they wouldn't
Speaker 1: close their leaves in spons So, given what we know
Speaker 1: about plants senses, communication, nervous systems, and memories, should we
Speaker 1: consider them to be either conscious or intelligent? What about pain?
Speaker 1: Does the fact that plants react to danger indicate that
Speaker 1: they feel pain? Well, some scientists argue yes, while others
Speaker 1: loudly say no. Today's episode was written by Christian and
Speaker 1: produced by Tyler Clang. Brain Stuff is a production of
Speaker 1: I Heart Radio's How Stuff Works from more in this
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