Black plants and whether or not they're edible

[sailorhathor]

Hi, I'm working on a book that features aliens from a planet that orbits a red dwarf star. One of the theories I've read through research is that the plants on this planet would be black and dark purple. One of the sites that I read explained it this way:

As indicated in NASA studies announced in 2007, plants evolved under dim red dwarf suns or in

Comments

[learnsslowly]

I think the colour thing will be a complete red/ black herring. We know that non-toxic dark red/ black/ purplish pigments can exist.(Blackberries). The question is more what other chemicals can be present in the plants? Here are a few thoughts - by no means a definitive list.

Plants cannot run away (usually - if yours can, please ignore this bit) so assuming there are some kinds of herbivores present, it might well be that some or all of them are toxic, foul tasting, sting, are spiky - something to avoid being consumed - or at least consumed entirely. However, it could be that the chemicals toxic to herbivores from the ecosystem of that plant are not toxic to beings from another planet - the toxin may inhibit an enzyme that eg and Earthling does not have.
Heavy metals ions can inhibit enzymes in liver, kidneys, other organs etc. Do the plants concentrate these? Do the rocks have very high levels of eg Cadmium?

Toxicity may not be an all or none thing - plants could have toxins which can be destroyed by heat - if the toxin is a protein this isn't unlikely, or by acids or alkalis. There may be toxins in some parts of the plants and not others.

Making a toxic molecule will almost certainly have energy costs to the plant, so putting the plant in a position where it is protected from herbivores, doesn't need the toxin, and then using good old-fashioned artificial selection to develop a low toxicity variety may be a possible.

As far as nutrition is concerned you have a few options too. To get your head round this, Googling optical isomers may help you more than my brief explanation. Carbohydrates on Earth are based on one optical isomer of sugar - the D isomer I think - but best check. If the carbohydrates on your planet are based on the L isomer, it might be difficult or impossible for beings with enzymes that fit d isomers to metabolize l isomers. The first inkling may come from the undigested sugars not being absorbed effectively, lowering the water potential in the gut and causing diarrhea. Probably not flatulence though, as the Earth bacteria presumably also can't metabolize them either.
You could have a similar issue with amino acids and proteins.

And then there are vitamins.......

I'd say, decide what you what to happen for story purposes, and let that guide which of many possible scenarios you choose.

[sailorhathor]

Thank you, that gives me things to research that I can possibly use to my advantage.