Carnivorous wire grass a.k.a. Bloodgrass

Question

Inspired by Bonegrass and the local sawgrass I've started thinking about a new creation...

Bloodgrass.

Bloodgrass typically grows along the edges of watering holes and streams in tall dense thickets (approximately 3-5 feet tall). Bloodgrass looks, at a distance, very much like other tall grasses, but upon closer inspection the blades are incredibly thin.

Don't inspect it too closely. And under no circumstances should you touch it.

Bloodgrass when touched by an unwary animal is known to suddenly and inexplicably coil around the unsuspecting creature, as the animal struggles to get free the thin wire like blades of grass cut into the flesh... bleeding profusely the animal begins to struggle and is further ensnared as it touches more blades.

Should you stumble into a patch of bloodgrass, Don't Move. The grass's spring like coil won't be sufficient to cut you badly. Your only hope is to Remain Calm and Wait For Assistance

Bloodgrass is thought to have initially developed its bloody trap as a defense from herbivores, but the adaptation thrived as the plants that used this trick were substantially better fertilized.

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This is more or less a reality check question, is this plant believable?

Also...

How could the grass quickly go from a long, straight, thin blade to a fairly tight coil and then return to its original straight form after killing?

Answer 1

It is believable up to a point. Stronger animals should be able to pull free and some larger animals should have strong enough skin to withstand the grass with only minor scratches.

However, if the grass can work even with those restrictions, I have one other nasty to add to it. In southern California, we have an invasive species that is locally called "lion tail" or "pampas grass" it grows 1-3 meters tall before the weight of the fronds cause them to droop. It has one thing that most people don't know about. The leaves are covered in an oil that is an irritant. If you are cut by the grass, the cut will itch and burn. If you add that to your bloodgrass, victims will have a hard time calmly standing still.

I lived by that stuff when I was a kid and used to use it as a hideout. The trick is that the fronds only cut when you move your hand away from the base of the frond. So, when you grab or touch it, you must always move toward the center of the frond. Being careful with how you handle it will allow you to move through a patch unscathed, even if you are in short pants and short sleeved shirts.

So there might be some smaller animals that live in the bloodgrass that will pre-digest the food for the plant.

Answer 2

The bloodgrass using the blood as fertilizer is the only issue I see. There are plenty of plants that have moving parts (https://en.wikipedia.org/wiki/Mimosa_pudica) and plenty of grasses that are unpleasant to walk through (the pampas grass mentioned above, and i can vouch for many sedges having sharp edges)

So just combine those and you are good.

But ultimately this comes down to risk vs reward. For many carnivorous plants the only reason to go through the effort of catching prey is the extra nitrogen that unwary insects provide. The plants focus on prey that is easy to overpower on the limited energy budget that a nitrogen-starved plant has. Some pitcher plants occasionaly catch mice but those are the exception to the rule.

So basically the expended energy has to be balance against the amount of nitrogen gained. And blood doesn't contain a lot of energy until you completely bleed the animal in question and if that happens you get a corpse, which contains all the nitrogen you could ever need. But that now-corpse might do a lot of damage to your leaves while it bleeds out because that is not a quick death.

And you need to do this in a nitrogen starved environment because otherwise you get overtaken by the plants who don't bother with all that "hunting" sillyness.

So a grass that is sharp enough to seriously hurt? Yes
That moves towards movement? Sure.
That uses blood as a serious part of nutrition? Not sure.

Answer 3

It does not need to have the strength of steel to cut. Fiber is strong enough to inflict Paper Cut, adding poison, or nastier, bacteria to quicken death. The bacteria lives symbiotically with the grass. It will inject strong anti-coagulant that gives the name of Bloodgrass, where the patch of the grass is often covered red by the blood of its victim.

I doubt the coiling will be both strong and fast enough, because strong means thicker vine/leaf, and thick usually means slow. The closest plant I can find is Sundew. Animals can break free from the coiling, but the sharp edge will cause more cut, and making the wound area larger.

The vine/leaf will return to original form for the same reason other plant with Thigmonasty , that is turgor pressure returning to normal value.

Answer 4

is this plant believable

"Reacting" plants already exist (Mimosa pudica and, even more, Dionaea muscipula) and it is very easy to evolve thorns and blade-like appendages.

There are plants that develop enhanced grappling powers with the purpose of hitching a ride (or allowing their seeds to hitch a ride) on the local furrymobiles.

So it would have begun with a thorny plant being fertilized by blood, and the thornier, the more cutting and more aggressive the plant, the more blood it would have harvested. Silica-enriched blades are not uncommon either.

Bloodgrass is therefore perfectly feasible - it's almost guaranteed to catch the fancy of some botanist on Giedi Prime - and it would work.

But is it really convenient to go for the kill? The kill is not going to be instantaneous, and a beast might tear up a lot of plant in its struggle to free itself before dying. True that this would yield a lot more fertilizer, but the cost might be excessive.

The simplicity of it all almost guarantees that if it was really advantageous, it would have already evolved. So you need to come up of a way in which the "fertilizer" is a real boon to plants, and yet they still can thrive without.

As a compromise the grass might have a specific breakpoint so that an animal too small to be dangerous is retained, but a larger prey - unless lame or sick - can escape without too much of a struggle.

This might allow an intelligent creature to attempt escape by breaking the grass blades one at a time rather than tackling them all together.