My question is Can a plant or fruit evolve or be made to look as if it evolved to produce blood? I want to have a story well a benevolent super being not a god a being with powerful tech; transplanted vampires and other supernatural blood drinkers to another world. This superbeing wants the planet to appear natural to an outside observer and doesn't want the blood drinker to have to hunt other beings. So they create plants that grow blood. I was thinking of something like a tomato as the plant/fruit, but it could be anything that fits. So is there a way to explain the natural development of such a plant/fruit and how/why it would exist as a native plant before cultivation?
It's a good thing that your super-tech being is in charge
Because it's not a distant step to get to where you're going.
Plants wouldn’t have this red blood but they do have green, which would be the chlorophyll in their leaves, and if you look at the structure of a chlorophyll molecule it’s really similar to a hemoglobin molecule which makes our blood red. The main difference would be there’s a metal atom in the middle of each of those molecules, and in the case of plant chlorophyll it’s magnesium, which gives it a green color, and in our case it’s iron and that gives us a red color.
... Those molecules they’re going to do pretty different things, the job of the green chlorophyll is to trap sunlight, and the job of our red hemoglobin is to trap oxygen or let it go. So that’s trapping energy versus trapping molecules, so that’s different.
... Speaking of the hemoglobin thing, there are so plants that have, basically a type of hemoglobin. I found that out recently just accidentally. Ruth Smith, a microbiology professor at Paul Smith’s College, one of my colleagues, was recently preparing a lab to show these nitrogen-fixing bacteria in the nodules.
... beans and alfalfa, and clover these legume plants, and I’ve always heard of that. I’ve seen them before too, they look like little lumps on the roots of these things, and the plants make these little lumps to encourage soil bacteria to live there, and the soil bacteria make nitrogen compounds that then act like a fertilizer for the plant. So I thought, wow that’s nice, but I looked and found that one of them was red! Like bright, bloody-looking red.
... it almost kind of looked like meat. I said wow, what’s that? And she said, it’s the inside of a root nodule, and I said it looks like blood, and she said well it’s hemoglobin. Well it’s a kind of hemoglobin, related sort of to ours, and the reason is kind of the same reason we have hemoglobin in our blood, it’s to bind oxygen. (Source)
OK, that was a bit lengthy. Our take-away from that is the following:
The hemoglobin/hemoglobin-like substances in the fluids of plants and animals are very similar and generally do the same thing, except that one uses magnesium to trap/bind light for energy production and the other uses iron to trap/bind oxygen.
There is an example in nature of a plant (kinda) that uses something much closer to hemoglobin to bind oxygen to help plants get what they need most: nitrogen.
But that's also your problem. From Earth's perspective, plants need nitrogen and use light to get to the energy they need to grow. Animals don't need oxygen for that purpose. The old phrase says close only counts in horseshoes and handgrenades — and that's the problem you're having. You need a plant that isn't a plant. You need an animal that has roots.
If you're looking for an evolutionary explanation, that might be a challenge
The problem is that there's no great reason for a blood-bearing plant (oxygen-binding) to exist. It's an evolutionary complication that simply isn't necesary. It would limit the number of creatures that could feed off it, while a traditional plant has a great many more, meaning it has more value in the ecological tree than a blood-bearing plant would. Without the ability to move around, there's no reason for the more energy-dense oxygen processing power to exist.
But you don't have that problem. You don't explain why you need someone to believe the plant could have or did evolve. Frankly, anybody visiting the planet who might question the plants would already be very distracted by the evolutionarily impossible vampires and other supernatural blood drinkers.
From the perspective of the denizens of the world, the plants would be normal. Perfectly normal. From the perspective of someone visiting the world, unless they had a mountain of analytical equipment and very specialized knowledge with them, they'd see the plants as normal because they rationalize the existence of the not supernatural but completely natural blood drinkers on the planet. It would take time for someone to look at those plants and say to themselves, "wait...."
I therefore don't believe you need much more than I've given you
Plants have fluid that's similar to hemoglobin. Your super-tech alien tweaks a plant such that it uses an iron-based fluid rather than a magnesium-based fluid. Or, perhaps more accurately, it uses both. Since we know plants respirate O2 (to a degree), your new plants do it by "sweating" out the O2 that's delivered by the oxygen-binding, iron-using blood.
And I'm not sure a tomato is the better choice. Yes, it's red and it looks an obvious choice for a blood-slurping vampire... but I wonder if a cactus wouldn't do a better job? Meaty, would look cool with red veins, could be cultivated. Think "prickly pear."