This is a series on the blog where I write about plants that feature heavily in the plots of popular culture. Spoiler alerts apply to these, even though some of the series writes about things that are quite old. However, for this one, about “Gaurdians of The Galaxy”, spoilers definitely apply.
Note: I talk about the science behind trees in this post. I am not a tree biologist or physiologist. I’m taking my knowledge of how plants work and writing about it in a hopefully fun way.
In “Guardians of The Galaxy” over the weekend. One of the Guardians is Groot, a walking tree that is sort of intelligent but doesn’t speak English very well (or whatever it is they’re supposed to be speaking in the galaxy). It’s a fun movie overall, when the opening titles have an old school Walkman with Peter Quill dancing to Redbone’s ‘Come and Get your Love’, I had an inkling I was in for a pretty fun time.
I was particularly interested in seeing this when I heard that one of the Guardians is a walking tree. One that can branch and grow almost at will, extending his legs to grow taller, sprouting twigs, releasing luminescent pollen to light up a room, and even protecting his friends in a wooden cocoon. He has a face, but hasn’t mastered speaking as all he says in various intonations is ‘I am Groot’ (this is exactly how R2D2 is used in “Star Wars”, Chewbacca too come to think of it); other characters speak to him and the audience imagines what the beeps actually say). Groot can also flower at will, as when he produces a flower, a nice small, blue one for a little girl (which could be weird too….flowers are the reproductive organs of the plant after all).
Groot is far from the first walking tree in popular culture. There are the Ents from the ‘Lord of The Rings’ trilogy. They are interesting; like real trees, they live on time scales greater than those of humans and so take their time, having an extended meeting before deciding to go destroy Isengard. The Ents are also tree-farmers; maintainers of a forest that they can move around and have the trees follow them. It’s like all trees are Ents, and can transform and move about when roused.
There’s also a walking tree in the first series of the rebooted ‘Doctor Who’. The Doctor and Rose visit the year 5 Billion to witness the destruction of the Earth by an expanding sun and luminaries gather to witness the event, including a tree-woman from Cheem. She moves like a person, not really wooden at all. And in something relatively creepy to me, she gives away cuttings of her grandfather as greeting gifts for everyone. Would those cuttings grow into intelligent beings too? Or just be plants? And no human would do something like that…give a cutting of a relative as a gift. It’s one example of just how different and alien plants are.
So could Groot actually work, as an organism? Trees on Earth, as are all plants have a decentralized body plan. As Groot demonstrates repeatedly, he can branch, and grow in many directions at once at the rate of a super-weed or at least within human second-to-second time scales. So it’s a little hard to imagine a plant developing centralized senses (i.e. a head, like we have) although plants do have sophisticated sensors of their environments, including for light; as that, more than anything is essential for plants to know (Go look at my friend Johnna’s blog for a primer on Photosynthesis; a lot of the other light receptors plants have are designed to optimize the position of plants for photosynthesis).
Plants DO move. Bunchberry plants have a hair trigger pollen launcher; whenever they’re hit, or touched, the trigger gets tripped and pollen gets flung out of the flower. It’s a really fast biological response. Cucumbers and other viny plants grow in a circular motion until the vine finds something to cling onto, and then it coils around it, all plants ‘nutate’ or rotate in a circadian rhythm as they grow and of course, thigns like sunflowers famously track the light during the day, changing flower and leaf direction. Flowers can also close and open at various times. And of course, roots grow down into the soil. Venus flytraps can also close fairly quickly when triggered by prey.
Trees can be flexible and strong, though lignin; the complex molecule that gives wood it’s toughness, is not the most flexible substance ever. And Groot does have a certain stiffness about his movements.
The amazing thing about Groot is that he walks and runs and keeps up which implies the flexing of ‘muscles’, even though plants don’t really have those. They can expand and contract cells by changing water pressure inside of their cells, so perhaps some kind of hydraulic muscle system could evolve. The other thing I thought about with the fast growth responses Groot displays are just how many hormones must be coursing through his plant vascular (circulatory) system to promote and inhibit growth of plant cells that really cause directional changes in growing plant organs. Particularly the hormone auxin, which is involved in places.
It’s also not clear that Groot photosynthesizes; he doesn’t have a lot of leaves. However, plants also have mitochondria, celluar energy factories and it’s possible he’s evolved to metabolize more by respiration alone; although then there’s an issue because a large part of plant life is that they take carbon dioxide from the atmosphere and turn it into sugars that fuel the growth and provide the ‘stuff’ that the plant is made of (plants build themselves from the air! And I imagine Groot can eat things and is root system is his gut, absorbing water and other nutrients all plants need). So when Groot is extending himself quickly, just how much carbon is he burning through? Plants can store carbon in the form of starch, but they use those reserves during the night or seasons when photosytnthesis can’t occur (like the winter time). As far as I know, the activity of photosynthesis at night is quite low (e.g. star/moonlight are too faint to really significantly drive the process significantly, but I’m sure some is going on).
Groot sacrifices himself at the end and is smashed into a lot of pieces, but Rocket takes a cutting of him and the end credits show Groot slowly growing back. This is in fact, possible for plants to do. It’s possible to regenerate a whole plant from a single cell, so long as there’s a living cell there, the whole plant can re-grow. The new Groot will have the same genetics as the previous Groot, though it’s unclear whether he’d remember his past life. There is some evidence that plants can ‘remember’ things, even cross generationally largely via epigenetic mechanisms (chemical changes to how DNA is structured/packaged that don’t actually change the DNA sequence itself)…but it’s not a brain as such; and I’m having trouble figuring our just what a centralized plant brain would look like. It may not be impossible. It just means I haven’t thought enough about it. Groot isn’t the brightest bulb, it seems, so perhaps he has some sort of rudimentary brain that hasn’t mastered everything about the world for non-cellulose structured life.
Another funny thing about trees is that most of their biomass is in fact not living. Tree rings represent annual growth cycles, but those previous layers end being a structure for the living tree tissue to grow around (trees tend to get thicker as they get older). Groot can seemingly thicken and re-thin almost at will.
Groot is a fun character, and one that I hope gets people thinking more about plants and just how they work down here on Earth.
[Editor’s note: Things have been quiet around here. I’ve been busy living life, writing in other places and work has gotten hectic. Hope to be back to regular posting soon! ]