So How Did I Start Down the Sentient Plant Rabbit Hole of Research?
October is one of my favorite months of the year, because of Halloween and our annual Pumpkin Carving Party. This year would have been the 14th year that we hosted the party, but due to Covid we had to cancel. Yet, it got me thinking about killer plants. “But Jotham,” I hear you all screaming, “It’s October, and we want to hear about vampires or zombies or—”
For the party I carve, make cheese and home-brew!
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Well, I follow the rabbit hole of research where it leads me (and my education, I do have a PhD in Botany), and this month it leads me to Killer Plants! They’re green, They’re mean, but—Killer plants, really Jotham. Could plants take over the world—what would it take? What would we do? What’s that voice saying in the background?
“On the twenty third day of the month of September
In an early year of a decade not too long before our own,
The human race suddenly encountered a deadly
Threat to its very existence.
And this terrifying enemy surfaced,
As such enemies do,
In the seemingly most innocent and unlikely of places.”
Prologue “The Little Shop of Horrors” (song by: Jennifer Leigh Warren, Leilani Jones, and Sheila Kay Davis)
Okay, okay, let’s stop before we all start singing along to the lyrics of Little Shop of Horror. Yes, I’m talking about sentient plants. Not many things are scarier than a tendril grabbing at your ankle and dragging you into a thicket of leafy appendages. Besides The Little Shop of Horror, sentient plants have been used in sci-fi, horror, and fantasy stories. The sentient plants can arrive from space, laboratory grown, Middle-Earth, or possessed by demon. Some of my favorites include: Day of the Triffids, Invasion of the Body Snatchers, The Evil Dead, Lord of the Rings, Wizard of Oz, Attack of the Killer Tomatoes. So, could those innocent looking, oxygen producing house plants one day rise up and conquer Earth—let’s go down the Rabbit Hole of Research and find out.
The Scream! Matthew Bennell (Donald Sutherland)
Image by AtomicNumber14
Can Plants Move?
Perhaps the most familiar movement in plants, is the response to touch and the Venus flytrap (Dionaea muscipula) closes when an insect touches the flytrap's sensitive hair triggers. Besides the fly trap, other plants fold their leaves when touched, such as the mimosa tree (Albizia julibrissin) and oxalis houseplant (Oxalis regnellii and Oxalis triangularis). This type of movement is called nastic (from the Greek word meaning to press). Also, plant tendrils can respond to touch by curling itself around the surface
Plants also move in response to light, phototropism. This is where plants will follow a light source or the sun across the sky, like foxglove. Specialized hormones work to elongate one side of the plant faster than the other to cause the plant to bend and direct its growth toward or away from light.
Some plant movements are benign, like closing their petals at night, and all sorts of environmental factors can cause a plant to re-direct its growth, or “move”.
- gravity—geotropism or gravitropism
Read more about plant movement at the Penn State Extension Website.
Okay so plants technically can move, but can they, you know, walk? Let me introduce you to the walking palm tree (Socratea exorrhiza) found in Latin America. The walking palm has a very unique root structure, instead of having one central trunk, the palm splits into many smaller trunks and roots off the ground, which gives the appearance of legs. But can it move—legend and some scientist suggests the plam can move. The working hypothesis is: as light or soil conditions change, the palm can “kill off” some of its roots and grow new ones in the favorable area, hence over time moving. There are other bits of research that dispute this claim—Read More about this fascinating tree here.
Can Plants, Hear, Smell or See? And Can They Do Anything About It?
It has been shown that plants emit sounds when cut. After being cut or bitten, plants can release chemicals to poison the leaf munchers, alert surrounding plants, and even “call” other insects to come and help it. Read more about plants that feel pain here.
Plants also respond to aspirin (check it out), very similarly to humans. Aspirin like molecules (salicylic acid) and receptors are found in plants (salicylic acid-binding protein 2) and tell the plant to boost its immune responses.
Plants can feel, smell and hear approaching insects. It’s thought that Actin (key component in muscle fibers) is involved in the plants ability to sense its environment and may act in plants the same way as in muscles. An interesting article about plant senses.
Music and Plants
Many houseplant owner with a green thumb will tell you that talking to plants, and playing them music will help them grow. I’m guessing those beautiful green houseplants come more from regular watering and feeding than random musings. Yet, there is growing evidence that plants can hear their environment and respond. Yes, plants can hear themselves being eaten (think about that next time you’re munching on a salad—“Help me”—). Seriously, once plants hear themselves being eaten by an insect, they release chemicals which are unappealing. Plants can distinguish between similar acoustic sounds in the environment (such as wind, or their human roommates playing Wu-Tang Clan) and not deploy their defensive capabilities. Read more.
Image by AtomicNumber14
Can Plants See?
Humans only have two eyes and two types of photoreceptors (rods and cones) to see the world with, whereas plants have many types of photoreceptors (Arabidopsis has eleven). Unlike humans where light is comfort, for plants light is food and essential to survival. Because plants are mostly stationary they have to take in more information about their environment and respond to changes.
If Plants Can Move, See, Hear, Smell—Can They Think?
Plants do not have a central nervous system or brain like humans. But plants do use electrical signaling, like a nervous system (physiologist John Burdon-Sanderson proposed it as a mechanism for the action of the Venus flytrap as early as 1874). More recently glutamate receptors have been discovered in plants.
Glutamate is an important neurotransmitter in the central nervous system, and appears to have the same role in plants, except, as I mentioned, plants do not have nervous systems. Or do they?
So, can plants think? Are they intelligent? Maybe not in a human-centric way, but the idea of plant-intelligence is gaining traction. Law makers in Switzerland are trying to set guidelines designed to protect "the dignity of plants". Check out this Nature article.
What’s It All Mean? Are Killer Plants Coming For You, Barbara?
So, it seems plants are far more complex than we think and humans may have more in common with plants than we know. But plants still have a long way to go before they wage war on the human race. Still you should keep an eye on those house plants, don’t forget to water and feed them regularly and maybe switch to soft rock, because Wu-Tang clan ain’t nothing to mess with. Until next time! Happy Halloween!
Hope you enjoyed this little trip down my research rabbit hole, and will join me next time as I reveal the actual factual science in fiction and fantasy.
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Question for you: What’s your favorite Halloween Monster Movie? I have a few in mind, tell me yours and I’ll check it out. Who knows I may even follow it down the rabbit hole. Email.
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