WEBVTT - Are Plants Conscious?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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<v Speaker 1>it's Christian Seger. So there's this old episode of Star

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<v Speaker 1>Trek called Wink of an Eye. You may have seen it.

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<v Speaker 1>There's this race of aliens that live in hyper sped

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<v Speaker 1>up acceleration. So when the crew of the Enterprise appears

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<v Speaker 1>to meet up with them, they seem so slow that

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<v Speaker 1>they're unable to move. Now, imagine that scenario. If you

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<v Speaker 1>were the aliens, wouldn't you assume humans were inert objects

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<v Speaker 1>with no consciousness. Now let's take this and apply it

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<v Speaker 1>to our relationship with plants. When we watch videos of

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<v Speaker 1>plant life sped up, we see their lively movement. But

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<v Speaker 1>even though plants move and respond to stimuli, they're not conscious. Right, Otherwise,

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<v Speaker 1>every time we ate vegetables, we'd be causing them pain. Wait,

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<v Speaker 1>wait a minute, can plants feel pain? Well? Okay, there

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<v Speaker 1>was this guy once. His name was Charles Darwin. You

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<v Speaker 1>might have heard of him, and he once proposed something

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<v Speaker 1>called the root brain hypothesis. He proposed that the tip

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<v Speaker 1>of a plant's root could act like a brain does

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<v Speaker 1>in some animals, receiving sensory input and directing movement. In

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<v Speaker 1>the years since Darwin made this proposal. There's been a

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<v Speaker 1>growing movement in science called plant neurobiology, and it debates

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<v Speaker 1>the way we think about plants and consciousness. Other scientists

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<v Speaker 1>hate this term, but who cares, because here's some of

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<v Speaker 1>the things we know about plants because of this really

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<v Speaker 1>unusual research. Let's start with plant senses. We know that

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<v Speaker 1>plants have a variety of sense some that can actually

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<v Speaker 1>act as analogs to our site smell, touch, taste, and hearing.

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<v Speaker 1>In fact, there's evidence that when plants hear the sound

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<v Speaker 1>of a caterpillar chewing on a leaf, they respond defensively

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<v Speaker 1>by producing chemicals like mustard oil. This happens even if

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<v Speaker 1>the sound is a recording and nothing is eating the plant. Creepy, right.

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<v Speaker 1>Plants can also communicate sometimes. Plant chemical production is like

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<v Speaker 1>a method of communicating with other plants. So here's an example.

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<v Speaker 1>That smell of freshly cut grass that we all know

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<v Speaker 1>that's actually a distress call to warn other plants of danger.

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<v Speaker 1>It's true in gardens, no one can hear you scream. Now,

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<v Speaker 1>when this distress call reaches other plants, they will also

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<v Speaker 1>emit the chemicals to warn their neighbors as well. And

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<v Speaker 1>these calls can even work on different species of plant.

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<v Speaker 1>For instance, a sage plant can signal a tobacco plant

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<v Speaker 1>to emit an odor that's not just to animals that

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<v Speaker 1>are eating the sage. All right, So you hear the

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<v Speaker 1>term plant neurobiology and you say, but plants don't have brains. Well,

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<v Speaker 1>one of the reasons why many scientists hate that term

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<v Speaker 1>is because plants don't have neurons, but they do produce

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<v Speaker 1>neuroactive chemicals that act like those in the human brain.

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<v Speaker 1>Glutamate receptors form memories in humans, and they're also found

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<v Speaker 1>in plants, and some hormones are transported around plants similar

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<v Speaker 1>to how neurotransmitters move through animal brains. Likewise, some plants

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<v Speaker 1>are vulnerable to drugs that disrupt neurotransmitters in the human brain,

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<v Speaker 1>like prozac or meth amphetamines. They even produce their own ethylene,

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<v Speaker 1>which is possibly used as an anesthetic when they're stressed out.

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<v Speaker 1>Plants even have a kind of nervous system, and that

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<v Speaker 1>may allow information to travel around the plant via electrical

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<v Speaker 1>sick mills. So if plants have sort of brains, do

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<v Speaker 1>they remember stuff? Well, yeah, plants also have their own

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<v Speaker 1>kind of memory. In fact, there's a plant called the

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<v Speaker 1>Mimosa pudica plant, and it closes its leaflets immediately after

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<v Speaker 1>they're touched, but because this requires energy, the plant won't

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<v Speaker 1>do it if it's unnecessary. However, when researchers dropped potted

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<v Speaker 1>mimosas fifteen centimeters onto foam, the plants learned that the

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<v Speaker 1>fall wasn't dangerous, so they stopped closing their leaves. Even crazier,

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<v Speaker 1>after one month, the plants still remember that the drop

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<v Speaker 1>wasn't dangerous and they wouldn't close their leaves in response. So,

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<v Speaker 1>given what we know about plants, senses, communication, nervous systems,

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<v Speaker 1>and memories, should we consider them to be either conscious

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<v Speaker 1>or intelligent? What about pain? Does the fact that plants

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<v Speaker 1>react to danger indicate that they feel pain? Well, some

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<v Speaker 1>scientists argue yes, while others loudly say no. Check out

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<v Speaker 1>the brainstuff channel on YouTube, and for more on this

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<v Speaker 1>and thousands of other topics, visit how stuff works dot

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<v Speaker 1>com