Plant Monsters

[Darth Raptor]

As you know, plant monsters are a mainstay of many a sci-fi and fantasy franchise, but how feasible are they?

Would plants be able to evolve tissues analogous to the muscles and nerves in an animal, or would their cell physiology prevent that?

Would photosynthesis produce enough sugar to sustain animal-like levels of activity, or would the organism have to suppliment their diet with heterotrophy ala the venus flytrap?

I'm no botanist, but the biggest hurdle I can currently think are cell walls. Because of cell walls any hypothetical vegie-muscles would be hard pressed to do the expansion and contraction of real muscles. I don't know how that would relate to vegie-nerves though. There are undoubtedly more complications I can't think of.

[Admiral Valdemar]

As you know, plant monsters are a mainstay of many a sci-fi and fantasy franchise, but how feasible are they?

Would plants be able to evolve tissues analogous to the muscles and nerves in an animal, or would their cell physiology prevent that?

Technically, plants already have muscle analogues that work in real-time. The ion/water powered contraction of a venus flytrap is down to a specialised tissue that is able to open and close like that of an animal muscle, but far, far slower. It would be a stretch to have something like this be used extensively on a frame though.

Would photosynthesis produce enough sugar to sustain animal-like levels of activity, or would the organism have to suppliment their diet with heterotrophy ala the venus flytrap?

The general consensus is that for anything that acts as a predator or roaming herbivore, you need more than photosynthesis. All the energy intensive organisms rely on heterotrophy as opposed to autotrophy, simply because without human engineered chloroplasts, the efficiency is just too low and surface area too small for walking plants. It could be a good secondary energy network though, for use in times when stationary periods are required with little nourishment.

I'm no botanist, but the biggest hurdle I can currently think are cell walls. Because of cell walls any hypothetical vegie-muscles would be hard pressed to do the expansion and contraction of real muscles. I don't know how that would relate to vegie-nerves though. There are undoubtedly more complications I can't think of.

The only way around this is to make such walls more flexible like the plasmalemma, which of course would make them somewhat redundant given they're meant to be like steel I-beams in a building. If you want a real-life triffid or RE2 plant BOW, you're going to have to merge properties of plants and animals together to produce some weird organism. Since plants have no nervous system (at least, they react only to basic stimuli at a cellular level), this beast would be hard pressed to do much.

[Darth Raptor]

Is there anything about plant cell physiology that prevents them from conducting chemical and electrical signals like a neuron does?

[Admiral Valdemar]

They'd need neurones for starters. Without a dedicated network, they just have the standard ion based signalling used by every cell in existence. That is nowhere near fast enough. So no, you're asking for them to perform a task that can only be done via a CNS already in place. If you need millisecond scale reactions over metre distances, only insulated synaptic networks will work. Imagine if a human was controlled solely by hormones in the lymphatic system. Crossing the road would be an exercise in futility.

[LaCroix]

The ion/water powered contraction of a venus flytrap is down to a specialised tissue that is able to open and close like that of an animal muscle, but far, far slower.

A venus Flytrap SLOW? I had one and dang', that thing was fast in closing. It could catch flies!

[Admiral Valdemar]

I had one too (it died. Didn't eat flies.), but next to an animal muscle, it is horridly slow. Compare the simple blinking of your eye next to a flytrap's grapple mechanism and then consider there are animals out there that can move faster than that blink.

[Darth Raptor]

I know you need neurons (or, more accurately, the hypothetical plant equivalent). I'm asking if there's anything about plant cells that's so fundamentally different from animal cells that they couldn't evolve nervous tissue?

[Admiral Valdemar]

Not really (aside from the cell wall, which is the big difference), they only branched back all those MYA because one cell liked being in a static colony of simple nature, while the others specialised and lost any photosynthetic capability. I suppose if you engineered a plant to grow nervous tissue, it would work, but with what? You'd need animal muscles to make it feasible, and then you run into energy problems depending on how fast you want this to move.

[Superman]

I dunno, ever see "Little Shop of Horrors?"

[Admiral Valdemar]

How about Plant 42? If the acid seeping tentacle vines don't get you, the cheesy theme music will.

[Lagmonster]

I had one too (it died. Didn't eat flies.), but next to an animal muscle, it is horridly slow. Compare the simple blinking of your eye next to a flytrap's grapple mechanism and then consider there are animals out there that can move faster than that blink.

I currently own two, plus a pitcher plant (and there are special nitrogen-rich plant meals you can buy to put in their pots so thatthey'll never need to eat insects, but what'll kill them fast is a lack of moisture).

The timing on a venus can be very fast, but nowhere near as fast as you can be. To put it simply, you should be able to close your fist faster than a venus can move to catch a fly. Ironically, bladderworts have *much* faster and better traps, but then they operate on a smaller scale.

An example of specialized evolution in action, to be sure, but you won't see any man-eating versions out there. The reason? These types of plants are passive predators which rely entirely on being more solidly constructed than their prey; you could destroy a man-sized venus if you were caught in it, or a man-sized pitcher, or even a bladderwort (the only possible threat is the sundew, but even then I'd have to see that humans couldn't muscle their way out of a vat of honey first). Mine, for example, generally lose one leaf for every six they grow to prey tearing the leaf apart and escaping.

[Max]

So, we shouldn't have any fear of Triffids?